5:08 AM
A temporary comment in order to get the linked questions updated: What kind group can be realized as a Isometry group of some space?Martin Sleziak 57 secs ago

2 hours later…
6:57 AM
Apr 21 at 7:16, by Martin Sleziak
Recently created tags: main, meta.
Apr 21 at 7:18, by Martin Sleziak
Most frequent tag creators: main, meta.
For recently created tags, it might be useful to have also links to the post and the revision history: main, meta.
Similarly as checking the first revision with a given tag, I can also check the last one. Of course, this information is interesting mainly for tags which have been removed as some point.
Recently "cleaned up" tag: main, meta.
Most frequent tag "cleaners": main, meta.

7:59 AM
Here are some guidelines for the next few removals of , which can be of course amended or discussed.
mathoverflow.net/questions/257748 : add , , . Formatting edit: "Semigroup"->"semigroup" in title; End -> operatorname{End} in text.
mathoverflow.net/questions/254566 : replace with . Edits "Take Alternating" -> "take the alternating"; add spacings before opening parentheses; erase "Any hints".

@MartinSleziak is specific and hence would be useful. I think the tag is totally useless (normal subgroups are somewhat everywhere in groups, and the tag is used only a tiny number of times: 26, while there are 6000 group theory questions, and 400 questions and 1000 posts contain "normal subgroup". It should even be erased, I think)

8:18 AM
I agree that it is questionable whether the tag is useful. (I think that it could be useful if it was used consistently.) One think which can help to make people aware of this tag is to use it when some questions where it fits is added (or bumped) - that's the reason why I mentioned it.

mathoverflow.net/questions/249495 add , ; clean up the post (blank lines, new paragraph starting without capital, paragraph ending without period, Gal -> operatorname{Gal}, sin,cos with backslash, remove "!!!"...)

It seems that the tag was created in 2016, and the questions in this tag come from the same user. The tag exists at least since 2014, if not longer.

mathoverflow.net/questions/232468 : add , , change C, C, G to $C$, $C$, $G$
mathoverflow.net/questions/230143 : remove . Fix the title "Order-Perserving Bijection" ->"Order-preserving bijection". Add ref info; 2nd link S. Huczynska, N. Ruškuc, Well quasi-order in combinatorics: embeddings and homomorphisms. Surveys in combinatorics 2015, 261–293, LMS LNSer 424, Cambridge Univ. Press 2015; change 3rd link to arxiv.org/abs/1107.5070v2

8:42 AM
@MartinSleziak there are 12 questions with "protomodular", by some other users. The tag looks fine and at worst harmless. I still think that "normal subgroup" doesn't fit for a tag, for the same reason "subgroups" would be a poor tag. Since 2014 there's 3500 questions tagged and only 21 were tagged . So expecting a consistent use sounds hopeless unless triggered by a intensive retagging by editors (which I wouldn't find worthwhile).

3 hours later…
11:29 AM
I think both and might be suitable for "Transposition Cayley graphs are planar". I have added at least one of them - however, all five spote are already taken. (I guess this is somewhat similar to the above discussion - both tags in question are relatively small, it's unclear whether they are going to be useful.)
1

Consider the Cayley graph $G$ with vertex set the elements of the symmetric group $S_n$ and generating set the set of minimal transposition generators of the group $S_n$, that is the set $S=\{(12),(13),\ldots, (1n)\}$. Then, will the graph be always planar? The graph is easily seen to be biparti...

Re: there are 12 questions with "protomodular", by some other users. I am only getting 9 questions. However, the number of questions is not the most important factor when deciding whether a tag might be useful.
Also I don't have anything against . (In case that wasn't clear from my message.)

5 hours later…
4:46 PM
This question does not have any top-level tag (although is rather big): Do infinitely nested radicals have any applications? Would fit? Should be added?
1

There is a simple necessary and sufficient condition for a continued radical of the form $\sqrt{a_1 + \sqrt{a_2 + \dotsc}}$ to converge (where all terms $a_1, a_2$ etc. are nonnegative). Namely, that the sequence $n \mapsto a_n^{2^{-n}}$ should be bounded. This is known as Herschfeld's Convergen...