12:45 PM
I totally missed that this post was part of a huge community wiki big list, otherwise I would not have edited it. I usually reserve such edits for when I have enough time to make all possible minor edits in one go, so that the post is not needlessly bumped.

2 hours later…
3:11 PM
53

Because the theory of sheaves is a functorial theory, it has been adopted in algebraic geometry (both using the functor of points approach and the locally ringed space approach) as the "main theory" used to describe geometric data. All sheaf data in the LRS approach can be described by bundles u...

10

Recently, the following tag synonyms were created by a MathOveflow moderator: abstract-algebra $\to$ ra.rings-and-algebras, geometry $\to$ mg.metric-geometry and discrete-mathematics $\to$ co.combinatorics. You can see the new synonyms in the list of tag synonyms (Wayback Machine). The three tags...

There are only three questions tagged sheaf-theory+mg.metric-geometry.
23

De Rham decomposition theorem states that every simply-connected Riemannian manifold $M$ that admits complementary sub-bundles $T'(M)$ and $T''(M)$ of its tangent bundle parallel with respect to the levi-Chevita connection is isometric to the direct product of two Riemanninan manifolds $M'\times... 2 Let$f:X\to Y$be a smooth map between paracompact differential manifolds$X$and$Y$. Let$U$be an open and dense subset of$Y$. For any$y\in U$, let$f^{-1}(y)=F$be a generic fiber that is a submanifold of$F$. Assume the singular fibers are$F/\Gamma_t$, where for each$t\in Y\setminus U\$, ...

But for the other two, the most recent edit was before creating the synonym. (After all, the last one still shows the deprecated tag.)
@MartinSleziak I think your guess is correct, the editor must have intended to add the tag (their edit summary also says, "added a tag", in the singular), and the deprecated tag would have been automatically changed to . I don't think the last tag is suitable any more for that question.
How did you come across this instance? :) Were you going over the synonymized tags to see if they needed cleanup?
I have recently mentioned the deprecated tags in the main chatroom.
in MathOverflow, 11 hours ago, by Martin Sleziak
For comparison, one can see some stats on deprecated tags on MO here: https://chat.stackexchange.com/transcript/10243/2022/9/18
Specifically, one can find edits like the above from this query:
Sep 18, 2022 at 6:32, by Martin Sleziak
Total: https://data.stackexchange.com/mathoverflow/query/1193740/question-which-no-longer-have-the-deprecated-tags https://data.stackexchange.com/mathoverflow/query/1193741/removals-of-deprecated-tags-per-user
Posts with deprecated tags can be found using this query:
Sep 18, 2022 at 6:29, by Martin Sleziak
There are 633 questions with deprecated tags. The same list ordered by most recent activity.
At some point, I have collected all questions with deprecated tags here: Recent tag synonyms for deprecated tags. (Deleted question - only visible for 10k+ users.)
The intention was that users willing to help might use that list to see which question need to be edited and which have already been edited. But since something like this would mean a lot of bumping, I have deleted the question. (So for nobody edited the answers posted there - with the lists of such questions.)
And apart from deprecated tags, there are some other problematic tags which might occasionally need checking: chat.stackexchange.com/transcript/10243/2018/6/17 and chat.stackexchange.com/transcript/10243/2022/12/10