In his editing for the 1837 edition, Joseph Smith removed the redundant about here in Mosiah 10:8, although the redundancy is not particularly offensive. As discussed under Jacob 7:8, the original Book of Mormon text (as well as the King James Bible itself ) has a number of examples where the adverb for a phrasal verb occurs twice:
The last three examples quote Matthew 7:4–5, which has the repeated out in the King James translation. The editing tendency in the Book of Mormon has been to remove these redundancies (see the discussion under each example); the critical text will restore in each case the repeated adverb.
Summary: Restore the original repeated adverb about in Mosiah 10:8: “they were girded about with a leathern girdle about their loins”.