CONTEXT (PARALLELS WITH OTHER TALES/GRECO-ROMAN)
“Stranger, you are no longer what you were just now! Your cloak is new, even your skin! You are one of the gods who rule the sweep of heaven!”

The noble and enduring man replied: “I am no god; τί μ᾽ ἀθανάτοισιν ἐΐσκεις” (“why liken me to the immortals?”)
Though also see (Homeric Hymn to Aphrodite ~90f.)
Love seized Anchises, and he spoke to her: ‘Greetings, Lady, whichever of the blessed [μακάρων] you are Who come to this house, whether Artemis or Leto, Aphrodite, well-born Themis or grey-eyed Athena…’
~108:
Aphrodite Zeus’s daughter then answered him: ‘Anchises, most glorious of humans born on earth, Why liken me to immortals? I am no goddess [οὔ τίς τοι θεός εἰμι: τί μ᾽ ἀθανάτῃσιν ἐίσκεις], But a mortal and my mother a mortal woman [ἀλλὰ καταθνητή τε, γυνὴ δέ με γείνατο μήτηρ]. My father Otreus is famous…’

the first . . . to call himself a philosopher or lover of wisdom, was Pythagoras; for, said he, “μηδένα εἶναι σοφὸν ἄνθρωπον ἀλλ᾽ ἢ θεόν” (“no man is wise, but [only] God”)

S1:
Years later, the sophist Hippodromus of Thessaly was praised by “the Greeks,” who “compared him to some degree even with Polemo,” (καί που καὶ τῷ Πολέµωνι ὁµοιούντων αὐτὸν), evidently a very high form of praise. Hippodromus responded: “Why do you liken me to immortals?” (τί µ’ ἀθανάτοισιν ἐΐσκεις;). With this response, Philostratus comments, Hippodromus did not “deprive Polemo of being considered a divine man” (τὸν Πολέµωνα ἀφελόµενος τὸ νοµίζεσθαι θεῖον ἄνδρα [VS 616]). According to Philostratus, then, at least in later generations, Polemo was considered a theios anēr and one of the “immortals.”
(VS, Vitae Sophistarum, Βίοι Σοφιστῶν)
Homeric Hymn: http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0138%3Ahymn%3D5%3Acard%3D10
Pythagoras:
“i am no goddess” latin

Ovid, Virgil:
Ovid’s Sibyl merely sighs (14.129) and says what is true of Ovid’s characterization of the gods in general : nec dea sum — ‘I am no goddess’ (14.130).

“i am no [god, etc.]” roman
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Mark 10.17-18 reads as follows:
καὶ ἐκπορευομένου αὐτοῦ εἰς ὁδὸν προσδραμὼν εἷς καὶ γονυπετήσας αὐτὸν ἐπηρώτα αὐτόν διδάσκαλε ἀγαθέ τί ποιήσω ἵνα ζωὴν αἰώνιον κληρονομήσω ὁ δὲ Ἰησοῦς εἶπεν αὐτῷ τί με λέγεις ἀγαθόν οὐδεὶς ἀγαθὸς εἰ μὴ εἷς ὁ θεός

As [Jesus] was setting out on a journey, a man ran up to him and knelt before him, and asked him, “Good teacher, what shall I do to inherit eternal life?” And Jesus said to him, “Why do you call me good? No one is good except God alone.”
While Luke follows Mark’s dialogue verbatim [edit: ], it’s well-known that Matthew diverges from Mark quite drastically:
καὶ ἰδοὺ εἷς προσελθὼν αὐτῷ εἶπεν διδάσκαλε τί ἀγαθὸν ποιήσω ἵνα σχῶ ζωὴν αἰώνιον ὁ δὲ εἶπεν αὐτῷ τί με ἐρωτᾷς περὶ τοῦ ἀγαθοῦ εἷς ἐστιν ὁ ἀγαθός

And someone came to [Jesus] and said, “Teacher, what good thing shall I do that I may obtain eternal life?” And he said to him, “Why are you asking me about what is good? There is only one who is good…
“If Jesus is good and no one is good but God alone, then this implies that Jesus is God” (quoting Thielman). And indeed, some of the more confessional scholars take precisely this view – like Richard Bauckham, who writes that are Jesus’ words here “seem actually to disclaim divine identity, but for competent readers mean precisely the opposite” (emphasis mine).
Although a bit different – and more nuanced – than the prior views, Simon Gathercole (in The Preexistent Son) ultimately comes to a similar conclusion.
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Challenges to this view – in particular, one based partly on Mark’s potential reliance on a Greco-Roman topos of praise/deflection:
Plutarch, in De Se Ipsum 18, describes the logic of how public praise can elicit envy (φθόνος) in others:

ἐν τοῖς ἀλλοτρίοις ἐπαίνοις, ὥσπερ εἴρηται, τὸ φιλότιμον ἐξανθεῖ τὴν περιαυτολογίαν καί τις αὐτὸ καταλαμβάνει δακνόμενον καὶ γαργαλιζόμενον οἷον ὑπὸ κνησμοῦ δυσκαρτέρητος ἐπιθυμία καὶ ὁρμὴ πρὸς δόξαν, ἄλλως τε κἂν ἐπὶ τοῖς ἴσοις ἕτερος ἢ τοῖς ἐλάττοσιν ἐπαινῆται. καθάπερ γὰρ οἱ πεινῶντες ἑτέρων ἐσθιόντων ἐν ὄψει μᾶλλον ἐρεθίζονται καὶ παροξύνονται τὴν ὄρεξιν οὕτως ὁ τῶν πλησίον ἔπαινος ἐκκάει τῇ ζηλοτυπίᾳ τοὺς πρὸς δόξαν ἀκρατῶς ἔχοντας.

when others are praised, our rivalry erupts, as we said, into praise of self; it is seized with a certain barely controllable yearning and urge for glory that stings and tickles like an itch, especially when the other is praised for something in which he is our equal or inferior. For just as in the hungry the sight of others eating makes the appetite sharper and keener, so the praise of others not far removed inflames with jealousy those who are intemperate in seeking glory.
But just prior to this, Plutarch had outlined a strategy for how someone who is praised might deal with this so as to appear modest and minimize the potential envy of others (and this is highly relevant to the NT texts under discussion here):

εἰώθασιν ἔνιοι τοὺς ταὐτὰ προαιρουμένους καὶ πράττοντας αὐτοῖς καὶ ὅλως ὁμοιοτρόπους, ἐπαινοῦντες ἐν καιρῷ συνοικειοῦν καὶ συνεπιστρέφειν πρὸς ἑαυτοὺς τὸν ἀκροατήν: ἐπιγιγνώσκει γὰρ εὐθὺς ἐν τῷ λέγοντι, κἂν περὶ ἄλλου λέγηται, τὴν ὁμοιότητα τὴν ἀρετῆς τῶν αὐτῶν ἀξίαν ἐπαίνων οὖσαν. ὡς γὰρ ὁ λοιδορῶν ἕτερον ἐφ᾽ οἷς αὐτὸς ἔνοχός ἐστιν, λανθάνει λοιδορῶν μᾶλλον ἑαυτὸν ἢ ἐκεῖνον, οὕτως οἱ ἀγαθοὶ τοὺς ἀγαθοὺς τιμῶντες ἀναμιμνήσκουσιν αὑτῶν τοὺς συνειδότας: ὥστ᾽ εὐθὺς ἐπιφωνεῖν ‘σὺ γὰρ οὐ τοιοῦτος;᾽’ Ἀλέξανδρος μὲν οὖν Ἡρακλέα τιμῶν καὶ πάλιν Ἀλέξανδρον Ἀνδρόκοττος, ἑαυτοὺς; εἰς τὸ τιμᾶσθαι προῆγον ἀπὸ τῶν ὁμοίων. . . . τοὺς δ᾽ ἀναγκασθέντας ἐπαινεῖν αὑτοὺς ἐλαφροτέρους παρέχει καὶ τὸ μὴ πάντα προσποιεῖν ἑαυτοῖς, ἀλλ᾽ ὥσπερ φορτίου τῆς δόξης τὸ μὲν εἰς τὴν τύχην τὸ δ᾽ εἰς τὸν θεὸν ἀποτίθεσθαι. διὸ καλῶς μὲν ὁ Ἀχιλλεύς

ἐπεὶ δὴ τόνδ᾽ ἄνδρα θεοὶ δαμάσασθαι ἔδωκαν
And in translation:

some, when the occasion allows, are in the habit of praising others whose aims and acts are the same as their own and whose general character is similar. In this way they conciliate the hearer and draw his attention to themselves; for although they are speaking of another, he at once recognizes in the speaker a merit that from its similarity deserves the same praises. For as one who vilifies another in terms that apply to himself does not deceive the audience, which sees that he vilifies himself rather than the other, so when one good man commends another he reminds hearers conscious of his merit of himself, so that they at once exclaim “And are not you one of these?” Alexander by honouring Heracles, and again Androcottus by honouring Alexander, won esteem for themselves for similar merit . . . But those who are forced to speak in their own praise are made more endurable by another procedure as well: not to lay claim to everything, but to disburden themselves, as it were, of honour, letting part of it rest with chance, and part with God. For this reason Achilles did well to say

Since I by Heaven’s will have slain this man
Surely we could find plenty of other occurrences; even within the NT: for example, 1 Cor 15.10 might come to mind: “…I worked harder than any of them — though it was not I, but the grace of God that is with me.”

Cf. also 2 Corinthians 12 for other strategies of “deflection”/circumlocution:

1 It is necessary to boast; nothing is to be gained by it, but I will go on to visions and revelations of the Lord. 2 I know a person in Christ who fourteen years ago was caught up to the third heaven–whether in the body or out of the body I do not know; God knows. 3 And I know that such a person–whether in the body or out of the body I do not know; God knows– 4 was caught up into Paradise and heard things that are not to be told, that no mortal is permitted to repeat. 5 On behalf of such a one I will boast, but on my own behalf I will not boast, except of my weaknesses. 6 But if I wish to boast, I will not be a fool, for I will be speaking the truth. But I refrain from it, so that no one may think better of me than what is seen in me or heard from me,
That the author of Mark has utilized a similar sort of honor-shame topos – as at least one element of the story – seems secure. It’s suggested that if this verse were “dealing specifically with the honor-shame dynamic,” that this “interpretation doesn’t mean that the verse is intending to claim divinity of Jesus”.
Brian Gregg, in his article “’Why Do You Call Me Good?’: A Markan Riddle” (which I’ll quoting throughout), quotes Adela Yarbro Collins’ interpretation to illustrate “the general scholarly consensus concerning Jesus’ query”:
“First, [Jesus] distances himself from the address by asking, ‘Why do you call me good?’ Second, he explains why he refuses the characterization of himself as ‘good’ by stating, ‘No one is good except one, (namely) God.’” The presumption is that Jesus has objected to being called good. Apparently, he deems it inappropriate in light of the singular goodness of God.

Similar assessments can be found in others – e.g., James Dunn passingly comments that “The implication is clear that for Jesus God alone is worthy of worship and such devotion, because God alone is the source and definition of all goodness”; Suzanne Henderson cites Mk 10.17-18 to illustrate that “Mark seems to demur here as elsewhere in the gospel from an overt claim to Jesus’ divinity” (also citing “Mk. 1:11; 9:7; 14:36; 15:39, where the relationship between Jesus and God is characterized as father to son”); and, more equivocally, J. M. Robinson quotes Mk 10.17-18 as epitomizing his proclamation that Jesus “apparently had no Christology.” Very much in contrast to the views highlighted in my previous post(s), Gregg writes that “Whatever the nuance, modern interpreters are nearly universally agreed that Jesus’ intent was to ‘deflect acclamation from himself to God’” – also citing
R. Alan Culpepper, Mark (SHBC; Macon: Smyth & Helwys, 2007), 335. Others whose conclusions align with this assessment include (but are by no means limited to) Craig A. Evans, Mark 8:27-16:20 (Word 34B; Nashville: Nelson, 2001), 96; Morna Hooker, The Gospel according to Saint Mark (BNTC; Peabody: Hendrickson, 1991), 241; Larry Hurtado, Mark (NIBC; Peabody: Hendrickson, 1989), 164; Eduard Schweizer, The Good News according to Mark (Atlanta: John Knox, 1970), 210-11; Jonathan A. Draper, “Go sell all that you have. . . (Mark 10:17-30),” JTSA 79 (1992): 63-69; Steve Barr, “The Eye of the Needle—Power and Money in the New Community: A Look at Mark 10:17-31,” ANR 3 (1992): 31-44. The one exception to the rule appears to be Robert Gundry’s commentary on Mark: Robert H. Gundry, Mark: A Commentary on His Apology for the Cross (Grand Rapids: Eerdmans, 1993), 553.
However, it should be said that Gregg – whose article I quote from – instead follows Gundry and those others who favor a high Christological reading of the passages: citing, in much the same way, the verbal parallel with Mark 2.7, as well as the material that follows Mark 10:18, where Jesus tells the rich young man that in addition to following the Commandments in the Torah, he must follow him to inherit “eternal life.” In this, Gregg agrees that “The locus of authority has shifted from God’s sacred word to his own person” – which to him, must connect back with the original question of the pericope itself.
For example, this seems to be precisely what’s going on in places like Luke 11.27-28:

While Jesus was saying these things, one of the women in the crowd raised her voice and said to Him, “Blessed is the womb that bore you and the breasts at which you nursed.” But he said, “μενοῦν, blessed are those who hear the word of God and observe it.”
I’ve purposely left μενοῦν untranslated here (on the different senses of the word, cf. Fitzmyer 1985: 928); however, surely the relationship between the two statements in these verses is, at most, one of antithesis. Perhaps this is all hinting at a subversion of familial relations in favor of the new ‘family’ of Jesus’ disciples – similar to Luke 14:26 et al. – and thus we may be justified in translating μενοῦν in an adversative sense, as NASB/NET/ESV do (“On the contrary, blessed…” or “Blessed, rather…). More naturally, though, the praise is not really directed at Jesus’ mother, but simply Jesus himself – and this is simply another one of those occurrences where Jesus legitimately dissociates himself from a divine identity. One notes a contrast with other episodes in the gospels, e.g. the woman who anoints Jesus with expensive perfume. When the disciples protest about how the perfume could have been sold and the money given to the poor, Jesus responds that “She has done a beautiful thing to me,” and then that “you can help [the poor] any time you want; but you will not always have me.” Here Jesus seems to gladly embrace such veneration. (Interestingly, these words appear similarly in all three other gospels, but only in Luke is the woman explicitly identified as a ‘sinner’, but then ‘rewarded’ with her sins being forgiven – which prompts the onlookers’ response τίς οὗτός ἐστιν ὃς καὶ ἁμαρτίας ἀφίησιν. Again, cf. Mk 2.7.)
Also of interest here are things like John 8.50, where Jesus says ἐγὼ δὲ οὐ ζητῶ τὴν δόξαν μου· ἔστιν ὁ ζητῶν καὶ κρίνων (“I am not trying to get praise for myself. There is one who demands it, and he also judges”). Again, refer to Plutarch and the ὁρμὴ πρὸς δόξαν, etc.

But bringing this back around to Mk 10.17-18, vis-à-vis Luke 11.27-28: if the Lukan passage quoted above is a true parallel to the Markan one, then Jesus has virtually rejected the veneration.

We might say that this could simply preserve a quite primitive stratum of tradition. And as I said, our wanting to read the two “parts” of the Markan pericope together could simply be an artifact of wanting to find significance where there really is none; and it’s possible that the author of Mark simply didn’t realize that there may tension between the two parts (if there even is any). Also, FWIW, there’s other material in Mark, somewhat similar to this, that doesn’t seem particularly well-integrated into its current context (most recently, I suggested Mk 11.22-25 as one of these).
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Beyond Matthean Redaction 📜
Matthew 19.16-17 (NA27):

16 Καὶ ἰδοὺ εἷς προσελθὼν αὐτῷ εἶπεν Διδάσκαλε, τί ἀγαθὸν ποιήσω ἵνα σχῶ ζωὴν αἰώνιον; 17 ὁ δὲ εἶπεν αὐτῷ Τί με ἐρωτᾷς περὶ τοῦ ἀγαθοῦ; εἷς ἐστὶν ὁ ἀγαθός· εἰ δὲ θέλεις εἰς τὴν ζωὴν εἰσελθεῖν, τήρησον τὰς ἐντολάς.

NRSV translates this

Then someone came to him and said, “Teacher, what good deed must I do to have eternal life?” And he said to him, “Why do you ask me about what is good? There is only one who is good. If you wish to enter into life, keep the commandments.”
Philip Comfort, on his commentary on NT textual variants, lists these variants for Mt 19.16-17:

In his commentary on the variants of 19.17, he writes:
The first variant [=οὐδεὶς ἀγαθός εἰ μὴ εἷς ὁ θεός] is a natural translational expansion of the WH NU reading in that it supplies what is implicit—namely, that God is the only one who is good.

As for the second variant — only extant in Latin and Syriac, but which we can reconstruct in Greek as *εἷς ἐστὶν ἀγαθός, ὁ θεός — he suggests it seems to have been intended:

to follow the textual variant of the previous verse, which reads, ‘Good teacher.’ In fact, the same manuscripts support the same variants in 19:16 as in 19:17. But it is a manifest harmonization to Mark 10:18 and Luke 18:19.
And it’s secure that the variant of 19.16 (διδάσκαλε ἀγαθέ, not simply διδάσκαλε) is simply a harmonization to Luke. However, re: “The WH NU reading allows for the interpretation that Jesus could be referring to himself when he says, ‘there is one who is good’” (emphasis mine): while in previous posts, I’ve questioned the possibility that this is the author’s original intention, there is in fact another textual variant here, not mentioned by Comfort (due to its attestation solely in patristic witnesses), that’s of great significance.
William L. Petersen, in his article “What Text Can New Testament Textual Criticism Ultimately Reach?” (originally published in B. Aland and J. Delobel, eds., New Testament Textual Criticism), notes

When [Mt 19.17] is quoted c. 150 by Justin Martyr [Dial. 101.2], it has a rather different text:

εἷς ἐστιν ἀγαθός, ὁ πατήρ μου ὁ ἐν τοῖς οὐρανοῖς

One is good, my Father in the heavens.
Justin’s text is supported by Tatian’s Diatessaron, as well as Irenaeus, Hippolytus, and the Pseudo-Clementine Homilies.

(See the Appendix at the bottom of this post for the texts here, and more notes. These are also discussed in F. Stanley Jones, “The Distinctive Sayings of Jesus Shared by Justin and the Pseudo-Clementines,” p. 211f.?)
Continuing, Petersen writes that:
This is an extraordinary situation, for in strictly chronological terms, then, the oldest-known version of this Matthean pericope contains the phrase “my Father in the heavens.”

This is fascinating – though, to be pedantic, this reading (in Justin, Tatian, Irenaeus et al.) is only older than the earliest extant NT manuscript containing the verse (which is א [Codex Sinaiticus] – dated only to the 4th century).
In any case, Petersen continues:
it should be noted that the suppression of this indisputably primitive reading . . . solves the theological, the Christological problem caused by its inclusion. Jesus’ answer, which clearly indicates that he is not ὁμοούσιος [of the same nature] with the Father—indeed, that he is not even a δεύτερος θεός [second god], as Origen termed him—is clearly unacceptable to later theological tastes. This objectional aspect of Mark’s text is cleverly redacted away by Matthew, who relocates the offending adjective “good”: in Matthew the young man asks, “[Teacher], what good deed must I do …,” not the Marcan “Good [teacher]”—the phrase which incites Jesus’ self-disclosure as a mere man. The fact that the Gospel of Matthew displays other evidence of redactional activity for Christological purposes in this same pericope, and the fact that this activity took place at such an early date that it has left no trace in the manuscript tradition, corroborates our deductions from our textual evidence. The variant found in our Patristic sources must also be very early and, just like the Marcan reading redacted away by “Matthew,” this reading was also excised because it was no longer theologically acceptable.
(A couple of observations on this)
Michael W. Holmes, in his article “Text and Transmission in the Second Century” (in the volume The Reliability of the New Testament: Bart D. Ehrman and Daniel B. Wallace in Dialogue) critiques Petersen here. He writes:
The two preceding phrases [in Justin’s text], “good teacher” and “why do you call me good,” reflect Mark and/or Luke, not Matthew. Furthermore, Justin is known to have used a harmonized collection of sayings of Jesus, one that was based on multiple sources in addition to Matthew, Mark, and Luke.
For this he produces an extended list of citations:
On Justin’s use of multiple sources, cf Oskar Skarsaune, “Justin and His Bible,” in Justin Martyr and His Worlds, ed Sara Parvis and Paul Foster (Minneapolis: Fortress Press, 2007), 64–68; differently T K Heckel, Vom Evangelium des Markus zum viergestaltigen Evangelium [From the Gospel of Mark to the Fourfold Gospel], WUNT 120 (Tübingen: Mohr Siebeck, 1990), 326–27 On Justin’s use of a harmonized sayings collection, cf Arthur J Bellinzoni, The Sayings of Jesus in the Writings of Justin Martyr, Supplements to Novum Testamentum 17 (Leiden: Brill, 1967), 49–100; Leslie L Kline, “Harmonized Sayings of Jesus in the Pseudo-Clementine Homilies and Justin Martyr,” ZNW 66 (1975): 223–41; Koester, Ancient Christian Gospels, 360–402; William L Petersen, “Textual Evidence of Tatian’s Dependence upon Justin’s ‘ΑΠΟΜΝΗΜΟΝΕΥΜΑΤΑ,” Novum Testamentum 36 (1990): 512–34; Petersen, Tatian’s Diatessaron, 27–9; Craig D Allert, Revelation, Truth, Canon and Interpretation: Studies in Justin Martyr’s Dialogue with Trypho (Leiden: Brill, 2002), 195–202; G N Stanton, “Jesus Traditions and Gospels in Justin Martyr and Irenaeus,” in The Biblical Canons, ed J -M Auwers and H J de Jonge (Leuven: Leuven University Press, 2003), 353–70, esp 364–65 (repr., Jesus and Gospel [Cambridge: Cambridge University Press, 2004], 92–109); differently (but unpersuasively) G Strecker, “Eine Evangelienharmonie bei Justin und Pdeudoklemens [sic: Pseudoklemens]?” Novum Testamentum 24 (1978): 297–316 There is no indication that this harmonized sayings source was a complete gospel or meant to replace earlier gospels: cf Graham N Stanton, “The Fourfold Gospel,” Novum Testamentum 43 (1997): 329–35 (repr, Jesus and Gospel, 75–81), contra Koester, “Text of the Synoptic Gospels,” 28–33
The immediate question that comes to mind is: if the addition of ὁ ἐν τοῖς οὐρανοῖς is a harmonization – with what has it been harmonized (and why)? [I’ve now discussed this further below]
Petersen also notes in his article that
The historical fact that Justin, Origen, and all the early Fathers were adoptionist or subordinationist (as was the early church in general) agrees with the textual tradition under consideration here: the earliest recoverable text agrees with the earliest known theology: both are subordinationist. This subordinationist element disappears as we slouch towards Nicaea.
But that the variant happens to agrees with this theological Tendenz does nothing to prove its originality. In fact, one could argue quite the opposite. One wonders if there’s an instructive parallel with the case of the Trinitarian formula in Mt 28.19 here, which is similarly mired in hot theological controversy; and, as 28.19 is missing from Eusebius, H. Benedict Green uses this (among other things) to argue was a secondary development (“Matthew 28:19, Eusebius, and the lex orandi”)

the phrase (ὁ πατήρ μου) ὁ ἐν τοῖς οὐρανοῖς is virtually identical to ὁ πατὴρ ὑμῶν ὁ ἐν τοῖς οὐρανοῖς, found in Mark 11.25—the only difference, of course, being that the latter is directed to someone else (ὁ πατὴρ ὑμῶν), while the former has “my father.”
It should also be noted that the “father” being specified as “in (the) heaven(s)” is also characteristically Matthean phrasing: Mt 5.48 has ὁ πατὴρ ὑμῶν ὁ οὐράνιος; Mt 18.10 and 14 have τοῦ πατρὸς μου τοῦ ἐν οὐρανοῖς and τοῦ πατρὸς ὑμῶν τοῦ ἐν οὐρανοῖς, respectively (some mss. have τοῦ πατρὸς μου as well for the latter); Matthew’s version of the Lord’s Prayer has πάτερ ἡμῶν ὁ ἐν τοῖς οὐρανοῖς (Mt 6.9), as opposed to Luke’s simple πάτερ.
As said above, Holmes argues that in Justin’s text, ‘“good teacher” and “why do you call me good,” reflect Mark and/or Luke, not Matthew’. It should be noted, however, that this language is in fact absent from the Lukan parallel (10.25), which only reads:
Καὶ ἰδοὺ νομικός τις ἀνέστη ἐκπειράζων αὐτὸν λέγων Διδάσκαλε, τί ποιήσας ζωὴν αἰώνιον κληρονομήσω;
Further, we have asked above why ὁ ἐν τοῖς οὐρανοῖς was included at all.

Again, as noted, the 2nd century reading ὁ πατήρ (μου) ὁ ἐν τοῖς οὐρανοῖς is also Markan language (Mk 11.25-26). (I put μου in parentheses because the Markan Jesus doesn’t use “my father.” About the closest that comes to this is Mark 8:38, if Son of Man there is to be understood as a self-reference.)

In light of this… is it possible to suggest that, if Holmes and others are wrong and ὁ πατήρ (μου) ὁ ἐν τοῖς οὐρανοῖς was original to Matthew’s text, that the Matthean author’s source for the clause ὁ ἐν τοῖς οὐρανοῖς was none other than an early version of Mark 10.18 itself, reading something like ὁ δὲ Ἰησοῦς εἶπεν αὐτῷ Τί με λέγεις ἀγαθόν; οὐδεὶς ἀγαθὸς εἰ μὴ εἷς ὁ θεός, ὁ ἐν τοῖς οὐρανοῖς — a reading that was later removed from the manuscripts (of Mark)?

Granted, the phrase ὁ θεός, ὁ ἐν τοῖς οὐρανοῖς would be slightly unexpected considering its parallel in Mk 11.25, ὁ πατὴρ ὁ ἐν τοῖς οὐρανοῖς; though for parallel epithets using θεός, see Rev 11:19 (ὁ θεός ὁ ἐν ὁ οὐρανός); Revelation 16.11; the beginning of the Shepard of Hermas (ὁ θεὸς ὁ ἐν τοῖς οὐρανοῖς…: “The God who dwells in heaven and who, for the sake of his holy church, created, increased, and multiplied that which exists out of that which does not exist…”); Daniel 2 (ὁ θεός τοῦ οὐρανοῦ); cf. also John 3.13. (Also, see my comment at the end of the paragraph after the sentence that follows this one.)

Certainly it’d be too much to suggest that an early Markan reading here was …ὁ θεός, ὁ πατήρ [ὁ] ἐν τοῖς οὐρανοῖς—though interestingly, Origen has a version of the/a verse that reads somewhat like this. (Οὐδεὶς ἀγαθὸς εἰ μὴ εἷς ὁ θεός, ὁ πατήρ.)
While admittedly these are unlikely, there actually is manuscript evidence of a comparable removal of material that also suggests the subordination of the Son. The most (in)famous of these is in Matthew 24.36, where significant manuscripts remove the “Son” from the list of those who do not know the date of the eschaton (and Codex Monacensis and various Vulgate mss. do this for the parallel in Mark 13.32). Further, in light of εἰ μὴ εἷς ὁ θεός in Mark 10:18, it might be useful to point out that Mark 13:32 has εἰ μὴ ὁ πατήρ; so there’s precedent for an interchange of “God” and “Father” in similar phrases in Mark. (Also interesting little fact is that Mark 13:32 is the only of instance of “the Father” in Mark.)
(As for a change from θεός to πατήρ in Matthew: I know nothing about Matthean redaction of instances of Mark’s “God”; though the author of course does appear to change “kingdom of God” to “kingdom of heaven.” Further — although I have a forthcoming article that suggests that Mk 10.18 is indeed to be understood as a rhetorical parallel to the deflections of similar figures in Greek and Roman texts — it’s probably too much to suggest that we can find parallels that the proposed Markan phrase may be modeled on: e.g. the line of Odysseus, οὐ . . . ἐγώ γε ἀθανάτοισιν ἔοικα, τοὶ οὐρανὸν εὐρὺν ἔχουσιν. So, while it’s likely that the original text of Mark 10.18 lacked ὁ ἐν τοῖς οὐρανοῖς, it is certainly still a possibility that the original manuscript of Matthew 19.17 included it.)
Post:
in the course at looking at these characteristically Matthean “father in (the) heaven(s)” phrases, I came across Mt 23.9: εἷς γάρ ἐστιν ὑμῶν ὁ πατὴρ ὁ οὐράνιος. Looking at the larger context, this seems extremely relevant for everything discussed here; and it’s unfortunate that I overlooked it until now (I also don’t remember other works I consulted mentioning it either):

[The “scribes” and Pharisees love] to have people call them ‘Rabbi.’ 23:8 But you are not to be called ‘Rabbi,’ for you have one teacher and you are all brothers. 23:9 And call no one your ‘father’ on earth, for you have one Father, who is in heaven. 23:10 Nor are you to be called ‘teacher,’ for you have one teacher, ὁ Χριστός. 23:11 δέ the greatest among you will be your servant. 23:12 And whoever exalts himself will be humbled, and whoever humbles himself will be exalted.
This passage certainly deserves more attention in light of Mt 19.16-17 (perhaps this has been done, but I’ve overlooked it – Yieh’s One Teacher: Jesus’ Teaching Role in Matthew’s Gospel Report seems like a decent candidate): to discern its Christology, possible intertextual relationships, etc. However, if – as mentioned above by Holmes – we assume that Justin’s ἀπομνημονεύματα τῶν ἀποστόλων was indeed a harmonized version of the gospels (which Tatian, the Pseudo-Clementine Homilies, et al. relied on), is it possible that these verses in Matthew 23 also contributed to the harmonization here?

The full text of Justin (Dial. 101.2), mentioned above, reads:
λέγοντος αὐτῷ τινος· Διδάσκαλε ἀγαθέ, ἀπεκρίνατο· Τί με λέγεις ἀγαθόν; εἷς ἐστιν ἀγαθός, ὁ πατήρ μου ὁ ἐν τοῖς οὐρανοῖς.
And Irenaeus’s text (Adv. Haer. 1.20.2) reads

Καὶ τῷ εἰπόντι αὐτῷ, Διδάσκαλε ἀγαθὲ, τὸν ἀληθῶς ἀγαθὸν Θεὸν ὡμολογηκέναι εἰπόντα, Τί με λέγεις ἀγαθόν; εἷς ἐστὶν ἀγαθὸς, ὁ Πατὴρ ἐν τοῖς οὐρανοῖς.

(One notices how Justin’s text has ὁ πατήρ μου, with μου missing in Irenaeus.)

Origen (CommJohn 1.254):

Καὶ τάχα τῇ αὑτοῦ δικαιοσύνῃ ὁ σωτὴρ εὐτρεπίζει τὰ πάντα καιροῖς ἐπιτηδείοις καὶ λόγῳ καὶ τάξει καὶ κολάσεσι καὶ τοῖς, ἵν’ οὕτως εἴπω, πνευματικοῖς αὐτοῦ ἰατρικοῖς βοηθήμασι πρὸς τὸ χωρῆσαι ἐπὶ τέλει τὴν ἀγαθότητα τοῦ πατρός· ἥντινα νοήσας πρὸς τὸν μονογενῆ λέγοντα «Διδάσκαλε ἀγαθέ» φησί· «Τί με λέγεις ἀγαθόν; Οὐδεὶς ἀγαθὸς εἰ μὴ εἷς ὁ θεός, ὁ πατήρ»

…Because he understood the Father’s goodness, he says to the only man who addresses him as “good teacher”: “Why do you call me ‘good’? No one is good except one, God the Father.”374

Origen, Princ. 2.13 (Butterf?), Latin:

So the Saviour himself rightly says in the Gospel that “none is good save one, God the Father’,” the purpose of this statement being to make it understood that the Son is not of some other “goodness’, but of that alone which is in the Father; … a denial that either Christ or the Holy…
Hippolytus, Haer. 5.7.25: εἷς ἐστὶν ἀγαθὸς, ὁ Πατὴρ ὁ ἐν τοῖς οὐρανοῖς (though see 7.31.6)

Clement, Strom. 5.10.63: εἷς ἀγαθὸς, ὁ Πατὴρ.

Ps.-Clem. Hom. 16.3.4: ὁ γὰρ ἀγαθὸς εἷς ἐστὶν, ὁ Πατὴρ ὁ ἐν τοῖς οὐρανοῖς. (or ὁ πατὴρ μου ὁ…?)

Vetus Latina MS e (Mt.): Unus est bonus, pater; VL Latina MS d (Luke): Nemo bonus nisi unus Deus pater

(The Diatess. (Ephrem, Commentary on the Diatessaron 15.9): ܚܕ ܗܘ ܠܡ ܛܒܐ ܐܒܐ ܕܒܫܡܝܐ; Unus est bonus, Pater, qui in caelo [est];. (Diat. 91?) Codex Fuldensis: Nemo bonus nisi unus Deus)

Ephrem:
[The Lord] fled from that by which people favored him, so that he might show that he had received this goodness from the Father through nature and generation, and not [merely] in name. “Only one is good,”9 [he said], and did not remain silent, but added, “the Father,” so that he might show that the Son is good in just the way that the Father is good.
Et quomodo renunciavit huic nomini is qui de seipso dixit. “Pastor bonus animam suam dat pro ovibus suis”?

Epiphanius, Pan. 42.11.17, Scholion 50: Μή με λέγε ἀγαθόν· εἷς ἐστιν ἀγαθός ὁ θεός

(Also appears in some old Armenian mss [?]; see also condemned by Didymus; mentioned by Ephrem [“to others he said, ‘I am not good,’ although he…”]; and ps-Athanasius or something, “About the Epiphany in…”?)
Conybeare: “Here Matthew’s text challenges reflection. An ancient corrector who” Lieu:, on Epiphanius etc.:
Someone said to him, “Good teacher, by doing what shall I inherit eternal life?” He (said), “Do not call me good; one is good, (God)”. He [i.e., Marcion] added “the father”, and instead of “You know the command- ments” he says, “I know the commandments.” (Pan. 42.11.17, S50) 65

The second part of Jesus’ reply here, ‘one is good’, is closer to Matthew 19.17, perhaps reflecting Epiphanius’ own remembered text. 66 Tertullian identifies the significance of this response for Marcion, but it is unclear how far he is quoting him, and it is notable that he does not use the term ‘father’: ‘But who is good (optimus) except, he says, the one God?’ 67 On the other hand, in the Dialogue of Adamantius the Marcionite Megethius does support the reading ‘Father’, ‘No-one is good except one, the Father’ (Adam. 2.18–19 [1.1]). 68
Fn:
68 At Adam. 92.25–32 (2.17) Adamantius cites the passage in the Lukan form, ‘No-one is good except one, God’.
Other patristic readings, + standard:

Justin, Apol 16.7:
καὶ προσελθόντος αὐτῷ τινος καὶ εἰπόντος· Διδάσκαλε ἀγαθέ, ἀπεκρίνατο λέγων· Οὐδεὶς ἀγαθὸς εἰ μὴ μόνος ὁ θεός, ὁ ποιήσας τὰ πάντα.
Cyril of Alexandria, Thesaurus 10:
On the one hand, let the discourse of theology [ôBò ŁåïoïaßÆò › oüaïò] be meditated upon, not at all as having to do with those [passages] in which he appears speaking as a man, but as having to do with the fact that he is from the Father, as Son and as God. On the other hand, it is to be ascribed to the economy with the flesh [τῇ οἰκονομίᾳ τῇ μετὰ σαρκὸς] when he now and then says something that is not fitting to the bare divinity considered in itself. Therefore when he, as a man, says that he is not good in the way that the Father is good (cf. Matt 19:17; Mark 10:18; Luke 18:19), this should be referred rather to the economy with the flesh, and should have nothing to do with the substance of God the Son.7 As noted by Boulnois, the most …
Arius:
… Blessed Pope, is this: We acknowledge One God, alone unbegotten, alone eternal, alone without beginning, alone true, alone having immortality, alone wise, alone good, alone sovereign
S1 on Eunomius:
He alone is true God (Jn 17:3), alone is wise (Matt 19:17 (so Migne ed., but Rom. 16:27 would be better)), he alone is good (Matt 19:17), alone is powerful (iTim 6:15), alone has immortality (iTim 6:15). The Son’s ousia is generated…
Fn:
Gregory Nyssa Con. Eunom. III. 67 (589), quoting E
Other Origen?
Origen grounds this conclusion in Scripture on Jesus’ remark to the rich young ruler: “No one is good but God alone” (Mark 10:18; PArch 1.2.13). He goes into more detail in his discussion of the parallel text in Matthew 19:17 in his Commentary on Matthew. There he says that “the good, in its proper sense, is referred to no one except God” (cf. Comjn 1.254). It is applied, however, “inexactly” to other beings and other things (ComMt 15.10). The Son and the Holy Spirit exceed all other … ComJn 13.151
Malina and Rohrbaugh bring this up in their book Social-Science Commentary on the Synoptic Gospels (pp. 190-191)

Mark 10:17-22 The man coming to Jesus here is not a hostile questioner as were the Pharisees in 10:2. The type of question he asks is one dealing with the dimensions of a morally integral way of life. Such questions are about how to be a morally complete person, pleasing to God and one’s fellow human beings. However, the man opens his question with a compliment, calling Jesus “Good Teacher.” In a limited-good society, compliments indicate aggression; they implicitly accuse a person of rising above the rest of one’s fellows at their expense. Compliments conceal envy, not unlike the evil eye. Jesus must fend off the aggressive accusation by denying any special quality of the sort that might give offence to others. Such a a procedure is fully in line with the canons of the honor-shame interaction. The honorable person, when challenged, pushes away the challenge and diffuses any accusation that might fuel the position of his opponents. Here the counterquestion serves to ward off the unwitting challenge, while the proverb “No one is good but God alone” wards off the envy.
They’re saying nothing about divinity one way or the other. They’re dealing specifically with the honor-shame dynamic found in collectivist agrarian societies in the Ancient Near East.