The original manuscript is fully extant for a single had in Alma 31:8. The word immediately preceding this had is not completely extant in the original manuscript. The last letter of that word is partially visible; it does not appear to be a d, but it could be a y. In other words, the evidence is consistent with the hypothesis that the immediately preceding word was they. There is no room between extant fragments of 𝓞 for another had except by supralinear insertion; so it seems reasonable to assume that 𝓞 read “they had the word of God preached unto them”, not “they had had the word of God preached unto them”.
The use of the past perfective had at the beginning of the next verse, “they had fell” (or “they had fallen” in the standard edited text), definitely suggests that the text in Alma 31:8 should read “they had had the word of God preached unto them” (see under Mosiah 4:1 for discussion of fell as the past participle for the verb fall ). It is quite possible that one of the had’s was dropped during the dictation process. There is considerable evidence that Oliver Cowdery occasionally omitted the perfective had in the manuscripts, if only momentarily:
(Two of these cases, Alma 44:8 and Helaman 16:1, are complicated; for discussion see under those passages.) Thus it is possible that in 𝓞 for Alma 31:8, Oliver accidentally omitted the perfective had as he took down Joseph Smith’s dictation (or possibly Joseph himself omitted it in his dictation). The 1920 LDS edition emended the text here by adding the extra had.
It should also be noted that there is considerable evidence that the perfective had has sometimes been accidentally added to the text, as in these examples from Oliver Cowdery (in some passages, there is at least one nearby perfective had that seems to have prompted the intrusive had; these passages are each marked below with an asterisk):
In these instances, the earliest textual evidence lacks the perfective had where readers might expect it.
One question here in Alma 31:8 is whether the word therefore in “therefore they (had) had the word of God preached unto them” refers to the Zoramites as dissenters or as Nephites. The verse as a whole, with its implication that despite earlier preaching the Zoramites “had fell into great errors”, suggests that the therefore refers to the fact that the Zoramites were originally Nephites. Under this interpretation, the reader definitely expects “they had had the word of God preached unto them”. This interpretation is, in fact, explicitly supported by Amulek’s later language in Alma 34:2: “yea I know that these things were taught unto you bountifully before your dissension from among us”.
Another example where the editors for the 1920 LDS edition supplied the past perfect had is found at the beginning of the book of Alma:
As explained under that passage, the Book of Mormon text sometimes allows the simple past tense when readers expect the past perfect, as in this example from the book of Mosiah:
Thus the critical text will accept the occasional use of the simple past tense (as in Mosiah 27:8, Alma 1:1, and Alma 31:8) instead of the past perfect that readers might expect.
Summary: Restore in Alma 31:8 the earliest reading without the perfective had (namely, only the main verb had in “they had the word of God preached unto them”); although this reading could be an error for “they had had the word of God preached unto them”, the simple past-tense form is sometimes used this way in the earliest text.