At the end of this verse, the 1920 LDS edition changed the verb were to was, presumably because there is no hypothetical or contrary-to-fact implication in this yes-no question. As discussed under 2 Nephi 2:16, the subjunctive were was used in earlier English more extensively than it is in modern English. There is still one example of the subjunctive “were it not so” in the Book of Mormon text, but in this example the implication is contrary-to-fact and it occurs as a conditional clause:
(The textual history of this passage is complicated; for discussion, see under Ether 3:9.) The expression “were it not so” is, to be sure, much more frequent in English as a conditional clause than as a yes-no question. For instance, on Literature Online , there are 76 instances of the conditional clause type but only one of the yes-no question type, namely:
It is very possible that the use of were in the yes-no question type is the result of the highly frequent conditional clause type. In any event, the occurrence of the were here in 3 Nephi 23:9 appears to be fully intended. Thus the critical text will restore the original subjunctive were, the reading of both 𝓟 and the 1830 edition.
Summary: Restore in 3 Nephi 23:9 the subjunctive form were in the yes-no question “were it not so”; subjunctive usage was considerably more common in Early Modern English and extended to cases where the expression was not hypothetical or contrary-to-fact.