According to John Gee, it should hardly surprise us that Nephi's and Jacob's quotations of Isaiah in the ancient text of the Book of Mormon do not break at our current chapter and verse designations. In Isaiah Scroll of the Dead Sea Scrolls, as well as Greek and other ancient biblical manuscripts, show that chapter and verse breaks were not present in ancient manuscripts. More recent hands, following the traditions of the rabbis and doctors, placed artificial divisions into the texts of these ancient scriptures. The division into chapters and verses that we now employ can be a subtle impediment to understanding the scriptures. . . .
When quoting lengthy passages, Book of Mormon prophets intentionally start and stop in certain specific places, reflecting natural breaks in Isaiah's text. Nephite writers normally marked breaks in passages through a syntactic or phrasal marker at the beginning of a new section. One of these is a statement of acknowledging the presence of a quotation . . . Jacob chose with care the long Isaiah passage that he quotes in 2 Nephi 6:6--8:25 (see 2 Nephi 6:4); he is not simply rambling on until he gets tired. Quotation statements mark the boundaries of the passage he quotes. The selection Jacob quotes from Isaiah contains four sections, each of which begins with the phrase "Thus saith the Lord: (2 Nephi 6:6; 6:17; 7:1; 8:22). [John Gee, "Choose the Things That Please Me": On the Selection of the Isaiah Sections in the Book of Mormon," in Isaiah in the Book of Mormon, pp. 68-69]