The above is related to my edit on this question and two answers there - this one and this one.

AFAICT adding links to post is considered useful. See also this meta post: Is it worth editing old posts to add links for references?

The answer by JDH is currently at the score 35.

Of course, since the post was bumped, I tried to do other improvements to question/answers which I noticed.

Since the tag normal-subgroups exists, I have added it. But I have admit I also have a feeling that it might be a bit too specific. Anyway the tag was here since 2014 and nobody objected to it so far.

So in a sense, if the tag should be removed, maybe my edit helped that more experienced users notice this tag and bring up possibility of removal of the tag in the relevant thread on meta.

I will add that I always keep the quota of no more than 3 edits per day. (I am way below this.) And when I edit something, I try to find what else can be improved - since the question has already been bumped.

TL:DR; The main purpose was to add links to papers. Since the post was bumped, I have also done some other edits.

AFAICT the main site is not flooded by edits to old posts.

I also know that users around here have various opinions on bumping old post (for example here is a discussion with Yemon Choi about this). My personal opinion is that bumping old post might be sometimes useful - a few more users notice the post. But I do my best to respect the customs of this site. (As I've said, I am way below 3 edits per day quote mentioned by François G. Dorais.)

TL;DR: I wouldn't do those edits if I did not consider them useful. Of course, I understand that different people might have different opinion on which edits are useful and which not.

BTW some time ago there was this suggestion about deprecated tags:

Another possibility would be to created tag warnings for those tags: Tag warnings on MO.

To me both these options seem reasonable. What others think about this?

And, of course, feedback on the normal-subgroups tag mentioned by YCor is also welcome.

specific-question The question Good Books about Large Cardinals probably should have some "book related" tag. Which tag would be suitable there?

On math.SE I would probably add both (book-recommendation) and (reference-request). I guess reference-request is suitable for this type of questions here on MO, too.

I am less sure about textbook-recommendation. Mainly because the word "textbook" in the tag name makes makes it sound a bit like a tag for questions about elementary/introductory text.

The tag-info says: "Questions asking for recommendations of textbooks on some subject. It can be helpful to indicate whether the request is for self-study, for use in a course one teaches, for use accompanying a course one takes etc., and to give some additional details on the context. Typically, additional tags are used to indicate the subject. ...

...For other questions on books, please use the tag books. If you are asking for a specific article, then reference-request tag may also be relevant."

And there is also the [tag;books] tag, which seems to be about something completely different: "Questions in which books play a key-role, such as questions on antique books, e-books, difference between various editions of a book, etc. For questions asking for recommendations of books on some subject the tag textbook-recommendation is often more suitable."

*books (<- to make it "clickable" - there was a typo in my previous message). Here is link to the tag-info.