Here the 1837 edition removed the repeated subject pronoun he. Such redundancy is characteristic of the original text, especially when there is some intervening subordinate text between the initial occurrence of the subject and its (pronominal) repetition at the beginning of the subsequent main clause. This kind of repetition has been sporadically removed throughout the text, as in the following nearby examples: Mosiah 8:7, Mosiah 15:22, and Mosiah 18:17 (see under each of these for discussion). For a complete list of this kind of redundancy in the original text, see under subject repetition in volume 3.
In his editing of this passage for the 1837 edition, Joseph Smith changed remaineth to remains in the printer’s manuscript. However, this change was not implemented in the actual 1837 edition, perhaps because in the next clause the verb hath was not changed to has; the two preceding third person singular present-tense forms (persists and goes) do have the standard-English ending -(e)s rather than the King James styled -(e)th. Another solution might have been to change the hath to has, so that all four occurrences of the third person singular present tense would have ended in -(e)s. The critical text will, of course, restore the mixture of endings found in the earliest text for Mosiah 16:5. For further discussion, see under infl al endings in volume 3.
Summary: Restore in Mosiah 16:5 the repeated subject pronoun he that occurred in the earliest textual sources; in addition, the critical text will maintain the original -eth ending for the verb form remaineth as well as the mixture of other third person present-tense forms in this passage.