@Asaf: I think you can find plenty of them here ... .

@AsafKaragila I dare to claim that there exist people who wouldn't even only need to spend one day of their personal income on this ... .

Wouldn't it mostly solve the problem without doing any significant harm if posts of new or unregistered users would be shadow banned until successfully having passed the "First Posts"- / "Low Quality Posts"- and questions also the "Close Votes" review queue?

@DavidRoberts When a question is reopened, the answers would of course be undeleted then (or at least it would seem strange to me if they would not ...). As to visibility of answers to authors of the questions, I don't see a reason to deviate from how things are now for deleted answers.

I don't see a need for a hardcoded way to suggest posting a question at Math.SE. Individual suggestions can be made in comments. -- And why not going a step further -- i.e. wouldn't just two close reasons "off-topic" and "no longer relevant" be sufficient -- where "off-topic" closure is only applicable to questions with no or only relatively new answers, and causes existing answers to be deleted immediately and the question to be deleted after some time if it is not reopened, and "no longer relevant" closure keeps everything intact and has no negative implications or connotation whatsoever?

If the problem is perceived to be serious enough to do something about it, then what about the following?: Make downvotes on a post be shown and have an effect on the post score only if there are at least three of them; if there are only one or two downvotes on a post and none are added to them within a certain time, then let them 'age away' by the time like close votes.

I think chat is anyway not a good place for a discussion on a particular post. In my opinion, such discussion should always be in the comments below the corresponding post. Rather than suggesting to move the discussion to chat, it would seem reasonable to me if the SE software would instead remind to polish the discussion afterwards (i.e. delete comments which are not interesting for future readers, etc.). Besides -- when I see the suggestion to move a discussion to chat, it usually either makes me stop it, or if it is sufficiently important, to continue it off-site (e.g. via email etc.).

Thank you. -- I think the post data confirms the "healthy steady-state" you already observed before.

How does this look like on a longer timescale -- say, the last several years?

@FrançoisG.Dorais: Yes, a dismiss button would certainly fix that.

So far I don't see a convincing reason to change anything in this respect at all.