Here we have one of the clearest examples showing that the 16-page signature (number 22) for the 1830 edition was proofed against 𝓞 rather than against 𝓟. The original manuscript is extant here and reads commander (the initial c is capitalized). When Oliver Cowdery copied from 𝓞 into 𝓟, he replaced commander with captain, probably accidentally. He was undoubtedly influenced by the two occurrences of chief captain in the preceding verse, both in reference to Moroni:
For a summary of the evidence that the 1830 edition was here proofed against 𝓞, see the discussion under Alma 42:31.
For the 1837 edition, the incorrect reading in 𝓟, chief captain, was restored to the text. This change was the result of the fact that 𝓟 rather than 𝓞 was used as the reference text for the 1837 edition. All subsequent editions have followed this reading. Elsewhere in the text, chief captain (as a singular) occurs eight times (including the two instances in verse 16). But chief commander is also found elsewhere in the text:
So there is nothing wrong with the use of chief commander in Alma 43:17, especially since this same title is used once more in Alma 46:11 to refer to Moroni. The critical text will restore in Alma 43:17 the reading of the original manuscript, chief commander.
Summary: In accord with the reading in 𝓞, restore chief commander in Alma 43:17.