Nephi would hear “isles of the sea” as a direct address. (See commentary accompanying 1 Nephi 19:10.) Nephi quotes this passage to his people to make explicit the application of this covenant to them.
In this verse, Yahweh affirms that he has honored their covenant in the past and continues to do so. As already noted, the servant might be several individuals: Isaiah, Christ, or Joseph Smith. Yahweh provides agents for Israel’s redemption to fulfill his side of the covenant.
Comparison: The Book of Mormon adds “O isles of the sea.” This phrase appears more frequently in the brass plates Isaiah than in the KJV Isaiah (Isa. 23:2, 24:15, 40:15). A second change is the addition of “my servant”: “… and give thee my servant for a covenant of the people.” Tvedtnes notes that the term “is very common in Isaiah and hence to be expected.” This change amplifies and provides a smoother reading than the King James Version.