The Book of Mormon contains 84 instances (by 15 different authors) of Epanalepsis or repetitive resumption. This editorial technique is used commonly in the Bible but was not known when the Book of Mormon was published.
Repetitive resumption is when the author repeats a phrase in order to bookend a specific thought or interject commentary and additional information. The repetition of the phrase would be a signifier for the reader that the additional commentary was over.
One example from the Book of Mormon is found in Alma 3:1:
And it came to pass that the Nephites who were not slain by the weapons of war, after having buried those who had been slain—now the number of the slain were not numbered, because of the greatness of their number—after they had finished burying their dead they all returned to their lands, and to their houses, and their wives, and their children
How would Joseph Smith know to include this technique if it was not known until recently?