@MartinSleziak Actually, looking at some questions like that, I wonder whether a tag like trivia (or maybe records or statistics) would be suitable for some questions here on MO.

Probably the fact that I bumped that question by removing the tag thesis lead to some people casting reopen votes - it is now in the review queue: mathoverflow.net/review/reopen/170264

BTW thesis is now down to 6 questions. So if the removal started with 13 question on December 3, it goes at the pace about 1 question per day.

So maybe I am doing the removals more-or-less in line with the promise I made.

What are som "problematic tags" on MO? chat.stackexchange.com/transcript/10243/2018/6/17

The deprecated tags abstract-algebra, discrete-mathematics and geometry are now in a kind of "limbo". I have posted some stats about the deprecated tags on September 18.

There are several tags that have been removed in the past - it might be worth checking from time to time whether some of those tags hasn't been created again. The ones I am aware of are arithmetic, calculus, classical-geometry, elementary, exact-solutions, inverse, proofs, representation, symplectic.

At the moment, there are no questions with those tags: mathoverflow.net/questions/tagged/…

The tag topology is somewhat special case - it was removed, created again, and now it is a synonym of gn.general-topology.

Maybe decomposition-theorem will be added to the above list at some point: chat.stackexchange.com/transcript/10243/2018/8/23

There are also a few tags that are often used incorrectly, so it is useful to check whether a question is tagged correctly if it has one of these tags. I was able to think of: books, covering, divisors, tag-removed, untagged, decomposition-theorem: mathoverflow.net/questions/tagged/…

Some other tags which should be included into the above categories?