The original manuscript has three supralinear insertions in this passage: “his rent coat” and “his brethren” (both set above in bold) and the subject pronoun he. Each of these insertions is written with somewhat heavier ink flow, which suggests that all three were added at the same time, probably at the time Oliver Cowdery read this passage back to Joseph Smith.
The he could have been missing from the original text (unlike the two longer insertions, which seem necessary). The immediately surrounding clauses also have the he (“and he took the pole … and he called it the title of liberty … and he prayed mightily”). Note, however, that earlier in this verse there is one conjoined predicate without the he (“and girded on his armor about his loins”). In that instance, the two conjoined predicates are closely associated (“and he fastened on his headplate and his breastplate and his shields / and girded on his armor about his loins”), whereas the conjoined predicates later on in the verse are semantically unrelated, thus making the initial reading less satisfactory (“and he called it the title of liberty and bowed himself to the earth”). The reference to bowing down belongs with the following predicate, which has the he (“and he bowed himself to the earth and he prayed mightily …”). The critical text will therefore accept the inserted he before the conjoined predicate “bowed himself to the earth”.
Summary: Accept in the original manuscript Oliver Cowdery’s inserted he in the middle of Alma 46:13; the insertion appears to be a correction to the original text, probably made when Oliver Cowdery read the text back to Joseph Smith.