Do Isaiah 66:23 and 66:24 contradict?

1. Benjamin Sommer in A Prophet Reads Scripture provides several references of scholars who think that both verses 23 and 24 are later additions to the passage, and briefly argues against this position. See the page here (page 246, “notes on pages 83-84”, note n°26. The paragraph the note refers to does not discuss Isaiah 66).
2. Unlike Sommer, Brueggemann (in this commentary) sees an opposition between verses 23 and 24, and thus posits that they are from different hands:

After the elegant hope voiced in 65:17–25 as promise to the “seekers after Yahweh,” this complex chapter returns us to the disputatious life of emerging Judaism. Although the glorious vision of Yahweh’s coming future may have been powerful and comprehensive enough to gain the assent of all parties in the community, the concrete response to the vision in practice evidently evoked deep disagreements. This chapter, seemingly made up of a series of smaller units, testifies to the fractured and fractious character of the community addressed by these texts. […] These final verses of the book of Isaiah pick up on themes we have already encountered. In verse 22a, the new heavens and new earth of 65:17 are recalled, a glorious vision of Yahweh’s large newness as sovereign over a fully healed cosmos. But in verse 22b that large vision is kept close to Jewish self-awareness, for it is “your descendants” and “your name,” referring to the chosen, covenanted community of Jews, who are guaranteed sustenance and maintenance.
In verse 23, the large vision of verses 18–21 is reiterated, for it is “all flesh” that are welcomed in worship. Indeed, from verse 21, we can imagine Gentiles presiding over the festivals of the Jews. But in verse 24, the focus is on the “rebellious,” the party in the community that has violated the requirements of nascent Judaism (see 65:2). These are the ones who will be slain by the sword (see v. 16). In a passion that sounds almost like contemporary ethnic hatred, moreover, it is not enough that they die. They must keep dying, endlessly destroyed, perpetually humiliated, everlastingly remembered scornfully. The lines are imaginative in their capacity to conjure ways to keep the polemic alive: worms to eat endlessly on their bodies, fire to burn endlessly in their bones. The final term, “abhorrence,” is used only one other time in the Old Testament, to speak of those who are raised to an eternal negative state: “‘Many of those who sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt’” (Dan. 12:2). No wonder Westermann can say, “This is the earliest idea of hell as a state of perdition” (Isaiah 40–66, 428). Interpreters observe that these final verses of the book of Isaiah exhibit a profound tension between magnanimous inclusiveness and intensely felt exclusiveness. It is evident, moreover, that there have been continuous, disputatious editing and additions to the book, as though each of the contending parties of inclusiveness and exclusiveness was determined to have one more say, and even to have the last say.
Clearly, the disputatious editing is not finished. It was not finished in ancient Judaism, which continued to struggle about the relationship between membership and serious torah keeping. The surest sign of the unfinished arrangement of the testimony is the later scribal note that in synagogue reading, after verse 24 is read, verse 23 must be repeated as the last word in order to overcome the venom of verse 24.
In a parallel example of edited prophetic writing, Schmid and Schroter in “The Making of the Bible” use Jeremiah 23:1-6. “A similar situation to that of the legal tradition also pertained to the books of the prophets. Here, too, pronouncements to which divine authority had been imputed needed to be updated, supplemented or corrected over time. Evidently, techniques from legal tradition were also used in prophecy. A prophet’s word was open to fulfillment, and it could even be fulfilled several times in succession. These events could then be recorded in updates of the prophecy. A virtual ‘chain of updates’ can be found, for instance in Jeremiah 23:1-6. It begins with a judgment in 23:1-2, which is couched in terms of a prophetic pronouncement and ends in a formulaic attribution of a divine dictum. It contains a judgment directed at the kings of Judah (shepherds), who are guilty of of having allowed their people to become scattered.”
“This passage is followed by a passage (Jer. 23:3-4) which is clearly written by another hand, for here, it is not the kings who have ‘driven away’ their people, but God himself. This passage makes it abundantly clear that the departure from Judah was not an error, but a part of God’s plan. The plan includes the subsequent gathering in of the diaspora.”

“The verses in Jer. 23:5-6 once more contrast with what preceded them. They specify that the new shepherd whom God will appoint to tend his people will be from the house of David.”

“These updates are not interpretations, in a narrow sense, of the text that precedes them, since they do not expatiate upon potential alternate meanings. Rather, the formulate new perspectives that transcend the content of the earlier pronouncement.”