Nephi’s comments are consistent with the comments and scriptures quoted above, and add a few insights. “The things of all nations” being known (v. 16) ties back to his foretelling of all the house of Israel being gathered and his “word also shall be gathered in one” (2 Nephi 29:12– 14).
All secrets and works of darkness being revealed (v. 17) was enlarged upon in a revelation to Joseph Smith in December 1832. Six angels shall each sound their trump and “reveal the secret acts of men, and the mighty works of God” in each of the six thousand years that preceded the millennium (D&C 88:108–110). The “sealed upon the earth” that are loosed (v. 17) probably refer to those who are in bondage to something or someone.
Satan having no more power over the hearts of men (v. 18) is worded slightly different in the Doctrine and Covenants; he “shall not have power to tempt any man” (101:28). As Nephi said previously, Satan has no power because “they dwell in righteousness, and the Holy One of Israel reigneth” (1 Nephi 22:26). In another revelation to Joseph Smith in February 1831, the Lord said, “Satan shall be bound, and when he is loosed again he shall only reign for a little season, and then cometh the end of the earth” (D&C 43:31). The “little season” will be at the end of the millennium. The “end of the earth” is the end of its mortal period before it is “sanctified from all unrighteousness, that it may be prepared for the celestial glory” (D&C 88:17–20).
“The end of [Nephi’s] sayings” (v. 18) was the end of his prophecies based upon the text of Isaiah. He does add a few words “concerning the doctrine of Christ” (see 2 Nephi 31:1–2 and the discussion in the next chapter).