Cultural: The practice of cutting off some body part as a token of conquest is not unknown in the history of the world. In the Old World, the practice was often used to count enemy dead or perhaps to more accurately pay mercenaries ("Ammon and the Cutting Off the Arms of Enemies." Reexploring the Book of Mormon. Salt Lake City: Deseret Book Company and FARMS, 1992, pp. 181-2).
Textual: There is no break in the 1830 edition. This is the introduction to Mormon's essential story, so he would not have made a break in the text at this point.