Here in the original manuscript, Oliver Cowdery initially wrote “do ye suppose that ye can convince the Lamanites of the traditions of their fathers”. Later, with distinctly heavier ink flow, Oliver supralinearly inserted incorrectness of the in 𝓞, giving what appears to be a much more reasonable reading: “do ye suppose that ye can convince the Lamanites of the incorrectness of the traditions of their fathers”. Oliver’s correction here may have been made after he read the text back to Joseph Smith and it was discovered that Oliver (or maybe Joseph) had skipped the phrase “of the incorrectness”. We might suppose that Oliver redipped his quill before making the correction; this would explain the distinct change in the level of ink flow for the correction. In other words, Oliver may have made this supralinear correction when he redipped his quill before taking down Joseph’s dictation later on in the next line of 𝓞, beginning with the relative clause “whose days have been spent in the grossest iniquity”. The level of ink flow is heavier for the inline text there, at least for the extant text beginning with spent (the second half of the relative clause). In other words, Oliver’s supralinear insertion of incorrectness of the in heavier ink flow could have come when he paused to reread the text back to Joseph. When the missing words were discovered, Oliver redipped his quill, made the correction, and then continued taking down Joseph’s dictation (also with the heavier ink flow resulting from the redipped quill).
But there is an alternative explanation for the corrected reading in Alma 26:24: namely, the supralinear insertion was the result of later editing on Oliver’s part. The initial reading in 𝓞 (“do ye suppose that ye can convince the Lamanites of the traditions of their fathers”) seems rather odd since one would think that the Lamanites, prior to their conversion, already believed in the traditions of their fathers and didn’t need to be convinced of those traditions. Thus one could argue that the corrected text (“do ye suppose that ye can convince the Lamanites of the incorrectness of the traditions of their fathers”) was the result of a later, conscious decision to emend the text.
There is one passage elsewhere in the text where the verb convince means ‘to prove or demonstrate as incorrect’ but without explicitly stating the incorrectness:
Of course, this passage does not mean that Ammon and his brethren convinced these Lamanites that their wicked fathers’ traditions were correct! To the contrary, they convinced the Lamanites that these traditions were incorrect. Yet this passage has never been emended so that it would directly mention the incorrectness of those traditions (although the adjective wicked in “the traditions of our wicked fathers” implies as much). In three other passages, the reference to incorrectness or wickedness is there but it is stated obliquely (that is, the Lamanites are convinced concerning their traditions, which are nonrestrictively characterized as incorrect or wicked):
In one place, the Lamanites are convinced of their sins and murders, with the implication that they are convinced of the evilness of those acts:
To be sure, there are passages where people are convinced of the incorrectness or wickedness of something—that is, in these passages the incorrectness or evilness is directly stated (as in the corrected reading for Alma 26:24):
Note that Helaman 5:19 and the corrected reading in Alma 26:24 are very similar except that one of them refers to the wickedness, the other to the incorrectness, of “the traditions of their fathers”. And there is also independent support for the phraseology “the incorrectness of the traditions of their fathers”:
Thus the corrected reading in 𝓞 for Alma 26:24 is quite reasonable.
The main problem with the initial reading in 𝓞 for Alma 26:24 is that there is no word at all that refers either directly or indirectly to the incorrectness or wickedness of the traditions of the Lamanite fathers. This special difficulty may have led Oliver to emend the text here at some later time. If so, the change was made, it would appear, before the text was actually copied from 𝓞 into 𝓟 since in 𝓟 the reading shows no sign of emendation (it simply reads without correction as “do ye suppose that ye can convince the Lamanites of the incorrectness of the traditions of their fathers”).
Ultimately, the decision here in Alma 26:24 is difficult. Probably the safest solution is to follow the corrected reading in 𝓞, which is also the reading in 𝓟, but with the understanding that the initial reading in 𝓞 may actually be the original reading.
Summary: Accept in Alma 26:24 Oliver Cowdery’s corrected reading in 𝓞 as the original reading (“do ye suppose that ye can convince the Lamanites of the incorrectness of the traditions of their fathers”), although there is some possibility that the supralinearly inserted words incorrectness of the, written in distinctly heavier ink flow, may be due to conscious editing on Oliver’s part.