Textual: These three verses continue the prophecy of Nephi that Mormon is applying to the marking of the Amlicites. In repeating these lines Mormon makes an interesting insertion. At the beginning of each of these lines Mormon adds the words “and again.”
What he is doing is emphasizing that this is a citation rather than his own words. The speaker of the citation is the Lord, and Mormon is both highlighting the specifics of the declaration and separating his voice from the voice of the Lord. Structurally, he ends the citation by the concluding “and these were the promises of the Lord unto Nephi and to his seed.”
We may assume that the written script on the plates followed general practices of ancient texts, and lacked the niceties of quotation marks, paragraphs, and indentations. In such a text, the verbal markers are more important than the written markers. It is also quite likely that the intent of writing was not necessarily reading, but reading aloud. In cases where the text was read aloud, structural markers such as these make it easier to follow the difference between citation and author’s narrative.