Since I've mentioned spam posts - the number of posts caught by SD in the last month is MathOverflow: 45, Mathematics: 54; All time - MathOverflow: 899, Mathematics 1589.

Maybe it is just my impression, but I have a feeling that I saw more spam messages on MO in the recent days than usually.

perhaps it's time for SE to require confirming username via an email.

@DimaPasechnik There was a discussion on meta about allowing posting questions only for registered users. The idea was rejected: Should MathOverflow require registration to ask a question?

And even if that was implemented, this would not prevent anonymous/unregistered users from posting answers.

The Mathematics site requires registration (for asking questions) - and spammers still mange to post spam also on Mathematics.

Mostly spam posts on MO are removed reasonably quickly (I'd guess under 10 or 15 minutes, but I do not know how to find precise data).

If the number of posts caught by SmokeDetector can serve as a reasonable approximation of the total number of spam posts, it's still under 100 questions per month - which is probably not that many.

It's quite plausible that many MO users do not know what to do when they see spam posts. I saw people interacting with spam posts as if they were serious posts, editing them, even creating (spam) tag.

Probably making a post on meta with an explanation how the spam posts are supposed to be handled might be a good idea.

Currently in the HNQ: Is There an Induction-Free Proof of the 'Be The Leader' Lemma?

So maybe it's not just my impression that now there is more spam on MO:

So according to 2018: a year in moderation the stats on MO are: "Question flags handled: 856, Answer flags handled: 830, Comment flags handled: 1,385."

Probably one expects as a typical scenario that somebody asks a homework/low-level question on MO and after they see that they are on the wrong site, they go to Mathematics.

This is an example of a user who asked first a question on Mathematics - since it was just a copy-paste of a problem statement (PSQ) it was put on hold. And then they asked on MO.

Relation between The Euler Totient& the counting prime formula (Mathematics); Relation between The Euler Totient& the counting prime formula (MathOverflow)

Clearly, in this case it did not help that the user had to confirm that they understand the rules when they asked on Mathematics.

I am mentioning this example partially in connection with this proposal: Should users be shown some basic information before posting the first question? (It was mentioned here in chat by Federico Poloni a few days ago.)