Here in both 𝓞 and 𝓟, Oliver Cowdery initially wrote “how strict is the commandments of God”; and in both manuscripts, he corrected the is to are by crossing out the is and supralinearly inserting the are. For the correction in 𝓟, there is no change in the level of ink flow; but in 𝓞 the supralinear are is written unevenly and with somewhat heavier ink flow. The correction in 𝓞 definitely appears secondary, and it seems highly unlikely that Oliver would have incorrectly written the are as is in 𝓟 if 𝓞 had already been corrected so noticeably to are. These two corrections, taken together, suggest that Oliver decided to correct the is to are as he was copying from 𝓞 into 𝓟. After correcting is to are in 𝓟 (this correction was virtually immediate), he then made the same correction in 𝓞. In other words, here in Alma 37:13 we probably have an instance of conscious editing.
Elsewhere in the text, there are 17 examples of the plural “how are ” and 5 of the singular “how is ”. In other words, for this expression there are no other instances that violate the standard rules of subject-verb agreement. In fact, none of these 22 instances show any variation in the grammatical number for the subject noun or any variation between is and are. In particular, there is no independent evidence that Oliver Cowdery ever accidentally wrote “how is ”. This systematicity argues that “how strict is the commandments of God” is probably not the result of a scribal error on Oliver’s part.
More generally in the text, we do find clear evidence in the manuscripts and in the 1830 edition for expressions where a plural subject is delayed and the preceding verb is the nonstandard is rather than the standard are. In the following cases, the original manuscript (where extant), the printer’s manuscript (before it was edited by Joseph Smith for the 1837 edition), and the 1830 edition all support the earliest nonstandard reading with is:
It is important to note here that Oliver Cowdery did not emend any of these instances of is to are. On the other hand, none of these are of the specific form “how is ”, which may have seemed particularly objectionable to Oliver.
Ultimately, here in Alma 37:13 the critical text will rely on the distinct difference between how the is was corrected to are in the manuscripts. The correction in 𝓞 is definitely secondary, which means that originally 𝓞 probably read “how strict is the commandments of God”. Thus the critical text will follow the difficult reading in this instance.
Summary: Restore in Alma 37:13 the original is that Oliver Cowdery wrote in 𝓞: “how strict is the commandments of God”; in this case, evidence from the manuscripts argues that when Oliver copied the text from 𝓞 into 𝓟, he decided to grammatically emend the is to are; he first corrected 𝓟, then made the correction in 𝓞.