Here the earliest textual source, the printer’s manuscript, reads Helem. Scribe 2 of 𝓟 initially misspelled the name as Helim, but then he immediately erased the i and overwrote the erasure with an e. This specific correction of the second vowel is a strong indicator that the original manuscript (not extant here) read Helem, not Helam. Based on the readings in chapters 18 and 23 of Mosiah, the spelling should be Helam, which is what the 1830 compositor set for this single occurrence of this name here in chapter 27.
As discussed under Mosiah 18:12–14 and Mosiah 23:19, Oliver Cowdery initially wrote every occurrence of the name Helam in Mosiah 18 and 23 as Helaman. For the three occurrences in Mosiah 18, Oliver’s corrections to Helam (by crossing out the final an) appear to be virtually immediate. In Mosiah 23, on the other hand, the 11 occurrences of Helaman were all later corrected to Helam, again by crossing out the final an but now with heavier ink flow. One wonders then whether 𝓞 actually read Helam in Mosiah 18 and Mosiah 23. One possibility is that 𝓞 actually read Helem but that Oliver, when he corrected all his instances of Helaman in 𝓟 (by simply crossing out the final an), systematically neglected to restore the original second e vowel in Helem and thus ended up consistently replacing Helem with Helam. There is one later instance of this same name in the text, and that instance also reads Helem in 𝓟 (for this example, 𝓞 is unfortunately not extant):
In this instance, John Gilbert (the 1830 typesetter) corrected 𝓟 by overwriting the second e in Helem with an a.
On the other hand, one could interpret these two later instances of Helem as scribal errors for Helam. The second vowel in this name is a stressless schwa; thus that vowel could have been easily misspelled in 𝓞. We could assume that the first use of the name was spelled correctly as Helam (in Mosiah 18:12) but that later in Mosiah 27:16 Oliver (the probable scribe in 𝓞 for the latter part of the book of Mosiah) misspelled the name as Helem. We have indirect support for this type of error in one other place in the original manuscript; in this instance, Oliver initially miswrote the name Helaman as Heleman:
In this case, Oliver’s correction was virtually immediate: there was no change in the level of ink flow when he overwrote the e with the correct a. Thus one could argue that in 𝓞 the name Helam could have been misspelled as Helem (at least in Mosiah 27:16 and in Alma 24:1). In addition, one could argue that the reason Oliver miswrote Helaman in Mosiah 18 and Mosiah 23 was that for those two chapters 𝓞 correctly read Helam rather than Helem.
This issue is further complicated by the fact that early on in the book of Mosiah there is another person whose name is spelled Helem in the printer’s manuscript (𝓞 is not extant here) and in all the printed editions:
Once more, various hypotheses suggest themselves. For instance, perhaps this first occurrence of Helem is also an error for Helam—one might argue that the name was misspelled as Helem because the following name Hem began with an h and ended in em. It is also possible, of course, that there are simply two different names, Helam and Helem, in the Book of Mormon. In the text there are other nonbiblical names that are spelled differently and refer to different individuals but are pronounced the same (at least in English):
Amaron Omni 1
Ammoron Alma 52 — Helaman 1
Ammaron 4 Nephi 1 — Mormon 4
Amoron Moroni 9
Cezoram Helaman 5–6
Seezoram Helaman 8–9
The text is also fairly balanced between Book of Mormon names ending in unstressed am and em; in addition to Helam versus Helem, there are five that end in am and four in em:
(The names Cezoram and Seezoram may be compounds based on the name Zoram: Ce +zoram and See +zoram.) For the name Ethem, we find further evidence for scribal confusion over how to spell a final unstressed /ßm/ syllable:
In this case, Oliver Cowdery initially wrote the name as Etham, but then almost immediately he crossed out the whole name and supralinearly inserted the correct Ethem (there is no change in the level of ink flow). The name Ethem occurs four other times in the book of Ether, and each of those other cases is correctly spelled in 𝓟 without variation as Ethem (none of these, including the one in Ether 11:11, are extant in 𝓞). The important point is that mix-ups have occurred in the manuscripts over whether to spell a final unstressed /ßm/ syllable as am or em.
Ultimately, the question comes down to two possibilities: (1) we could emend the first 14 occurrences of Helam in Mosiah 18 and 23 to Helem, based on two later occurrences of Helem in 𝓟 (in Mosiah 27 and Alma 24); or (2) we could follow the 1830 typesetter in his emendation of the two later occurrences of Helem to the earlier Helam. In my opinion, the simplest solution is to maintain the spelling Helam since it is the earlier one and there are so many more instances that support Helam over Helem. Of course, this decision applies only to the Helam that Alma first baptized at the waters of Mormon (and after whom the city and the land Helam were apparently named). On the other hand, the earlier Helem (found in Mosiah 7) is the name of a different individual (one of Ammon’s men). Thus the single occurrence of the name Helem for this particular individual will be maintained.
Summary: Accept the 1830 typesetter’s decision to emend the spelling Helem in Mosiah 27:16 and Alma 24:1 to Helam; maintain the earlier spelling Helem in Mosiah 7:6 since this refers to a different person and can therefore have a different spelling.