@IosifPinelis What regular users can use as criteria is e.g.: AI spammers are usually new accounts, very often unregistered; often they post a number of questions or answers within a short time, sometimes about quite different topics. Sometimes at least one of the posts made by the respective account looks "AI-like" in terms of style, formatting or particular formulations, or it contains mathematical mistakes a human mathematician hardly would make.

While I am not the moderator who destroyed this particular account, what I can tell is that often there are certain patterns in the data which is only visible to moderators which make quite clear that an account belongs to a series of accounts created to spam the site with AI-generated posts.

Just one observation: the vast majority of AI-generated posts appears to be by new unregistered accounts which do not give any clue about the identity of the person behind them.

In real-life social interaction, the ratio is rather the other way (it is said that about five positive interactions are needed to compensate for one negative one) — and my perception is that also on MO, many people tend to feel rather in that way, in spite of points. On the other hand, unfortunately some people really seem to take their gain of points for questions which receive more downvotes than upvotes as an indication that posting such questions is welcomed by the community.

@AndyPutman Done.

Have you checked that pages 141-147 of said book actually do not answer the question (in particular, as none of the regular MO users had flagged the answer so far, and as in your profile I do not see an indication that you are a mathematician)? -- The question owner has accepted the answer, and this happened 24 days after thanking the answerer in a comment. So, it seems to have happened not without taking some time to check. If you insist that the answer is spam (which is possible), then a bit more explanation is needed. Otherwise, the benefit of the doubt is with the poster of the answer.

I wonder when does a question count as being "closed by the community"? -- As to the above statistics, in 2023 it happened exactly 2 times ... .

To me, the question seemed a clear case for deletion (it is a question concerning decimal digits of a number which hardly relates to any interesting number theory, and it got downvoted and closed by the community). Since people other than the OP themselve disagree with this judgement, I undeleted the question again to leave the decision on whether or not to delete it to the community. -- Apologies for the inconveniences!

I think the circumstance that a question has been created by particular means neither contributes to making it on-topic nor to making it off-topic. What matters is solely the question as such itself.