Here in Alma 58:16, the original manuscript is not extant for either occurrence of the reflexive pronoun himself /themselves (listed above as 1 and 2), but spacing between extant portions of 𝓞 indicates that the original manuscript probably read himself in both instances. When copying from 𝓞 into 𝓟, Oliver Cowdery wrote the first himself correctly, but the second one he initially wrote as the plural themselves. He immediately caught his error and by supralinear insertion corrected themselves to himself (the level of ink flow is unchanged for this first correction). But at some later time, Oliver apparently decided to accept the plural themselves that he had originally written in 𝓟. This second correction was done with a different quill (or one that had been resharpened); the writing is somewhat sharper, and the ink appears slightly blacker.
This editing is odd because the first occurrence of himself in verse 16 was left unchanged. Except for the placement of the auxiliary verb should, the two clauses are parallel:
Perhaps the nonparallel when-clause in the next verse is the source of the themselves: “and when they had thus secreted themselves” (Alma 58:17). The committee for the 1920 LDS edition, of course, inherited a grammatically contradictory clause for Alma 58:16 (“Teomner should with a small number of men secrete themselves”), but instead of replacing themselves with himself (in accord with the earlier clause regarding Gid), the 1920 editors changed the preposition with to the conjunction and, which then forced the should to be moved after “and a small number of men” (giving “Teomner and a small number of men should secrete themselves”).
The original text treats each unit of the army (under Gid and Teomner) as a singular. Thus in verse 17, the earliest text reads “Gid and his men was on the right and the other on the left”. The singular other is the reading of the earliest extant source—that is, 𝓟 since 𝓞 is not extant for the word other(s). The ellipted form of the be verb for “the other on the left” would be the same singular was found in the preceding “Gid and his men was on the right”. Unfortunately, the 1830 typesetter missed the significance of the singular other and replaced it with the plural others.
One possible emendation in verse 17 would be to replace the and in “Gid and his men” with the preposition with, thus “Gid with his men was on the right”. This emendation is supported by the original usage in verse 16: “Gid with a small number of men should secrete himself” and “Teomner should with a small number of men secrete himself ”. Of course, the nonstandard use of the singular was with plural subjects is found in the original text, as in Alma 14:23: “unto the prison where Alma and Amulek was bound with cords”. For some discussion as well as examples of such usage, see under 1 Nephi 4:4. Thus there is no strong need for emending “Gid and his men” to “Gid with his men” in Alma 58:17.
The earliest reading in Alma 58:16–17 means that in the following clause (“when they had thus secreted themselves”), the plural pronouns they and themselves actually refer to these two units: (1) Gid and his men and (2) Teomner and his men. The plural usage does not refer to the individual soldiers themselves, which is what one might expect from the secondary themselves in verse 16 and the secondary others in verse 17. Thus the critical text will restore in every instance here the earliest extant reading, which makes perfect sense:
As already noted several times, there is considerable evidence in the original text for using the name of a military leader to stand not only for himself but also for the men under his command. See, for instance, the discussion and the examples listed under Alma 43:53.
Summary: The original text in Alma 58:16–17 treats each unit of Helaman’s army as a singular; the critical text will restore all the original singular noun forms as well as the original syntax: “and also that Teomner should with a small number of men secrete himself also in the wilderness / now Gid and his men was on the right and the other on the left”; there is no strong motivation for emending “Gid and his men” to “Gid with his men” since in the original text the verb form was can occur with plural subjects.