Separating verse 29:1 from verse 28:32 leaves “but behold, there shall be many… ” dangling, without a context, without a clear reason for the reversal implied in “but,” and without an obvious explanation of who the “many” are. Read with 28:32, however, the context is the Gentiles: “Wo be unto the Gentiles, saith the Lord God of Hosts! For notwithstanding I shall lengthen out mine arm unto them from day to day, they will deny me; nevertheless, I will be merciful unto them, saith the Lord God, if they will repent and come unto me; for mine arm is lengthened out all the day long, saith the Lord God of Hosts.”
Verse 28:32 condemns the Gentiles, unless they repent, while 29:1 promises that “there shall be many” repentant Gentiles. The rest of the verse explains when these repentant Gentiles will exist—during the last days when Yahweh will work to recover his people.
Redaction: An important narrative shift is the change in voice that occurs in this verse. Instead of Nephi recounting his prophecies, this passage is Yahweh speaking. This shift began in 2 Nephi 28:30 with his quotation from Isaiah. In the KJV Isaiah, Isaiah is speaking in his own voice; but in Nephi’s text, Yahweh is the speaker.
Of course, this revelation is from Yahweh, given through Nephi, but so were the revelations that Nephi recounted in the past tense in his own voice. This revelation is either a quotation or a revelation that Nephi is receiving as he writes. There is no way of knowing when Nephi received this revelation. It is certainly thematically related to the rest of Nephi’s discourse during this pesher on the Isaiah chapters. At the very least, the shift in the speaker allows Nephi to highlight themes that have already been presented but to do so in a slightly different context.