specific-question deprecated-tags I guess co.combinatorics would fit here: Hidden points in polygons. (We can consider discrete geometry as an area in the overlap of geometry and combinatorics.) So I have crossed this one out of the list. After merging discrete-mathemstics into co.combinatorics it would be correctly tagged.

In case somebody is willing to have a look, maybe it would be worth having a look at the rest of the list for discrete-mathematics. Mainly because one of the mods indicated that they might take some action on deprecated tags.

@S.Carnahan Since you're the moderator who created the synonym and also discussed the deprecated tags here for a bit, I will point out the above messages - in case you have time and want to look into this.

Here is the related post on meta: What to do with the synonyms for the deprecated tags? It also contains the link to our exchange in chat.

For the other two deprecated tags - geometry and abstract-algebra - the situation is worse. But in the case of discrete-mathematics, many questions have already been crossed out of the lsit.

Some stats: Questions which no longer have deprecated tags and Removals of deprecated tags per month.

@MartinSleziak On math.stackexchange there are too many, so I only changed a few. On MathOverflow there were only like a dozen, so I changed all or almost all links that are in posts, and usually left a comment when it's in a comment.

@FrançoisG.Dorais ^

I also edited them on some of the other SE sites, but I haven't checked all sites.

and I won't touch them in StackOverflow.

You're right - I did not even checked the other sites. There are 90 posts with URLs containing efriedma. And 73 posts with stetson.edu/~efriedma - so some in the first search are most likely false positives.

data.stackexchange.com/mathoverflow/query/1341643/… and data.stackexchange.com/mathoverflow/query/1341646/… are the queries to find the old links; you can change the site there the usual way

stackexchange.com/users/1192385/zsb%c3%a1n-ambrus?tab=activity shows my recent network edits: it shows I've edited stuff in MathOverflow, Math SE, Code Golf, Puzzling, Puzzling meta, Cross Validated, Sci & Math History, and Computer Science.

There are two annoying parts of this site change: one is that the old URL doesn't redirect to the new page, or even have a link to the top of the new site (I wonder why, perhaps ti's some weird policy of the univ that hosted it);

and that the Periodic Table has changed so that the same bibliographic entry got moved to a different element, and the URL has the element symbol only, so it's not trivial to find the new URL for the bibliography of a particular mathematician (this may have changed before the site migration, I didn't check).