@MartinSleziak deleted-tag Since the question was deleted, the tag recursion is gone.

deprecated-tags After checking how many users actually help with removing deprecated tags, it does not seem too likely that the number of posts with these tags is going to decrease quickly. Unless I made some mistakes in the SEDE queries, it seems that geometry is the only such tag where more than two users made significant contribution.

abstract-algebra data.stackexchange.com/mathoverflow/revision/1038474/1282557/… data.stackexchange.com/mathoverflow/revision/1038477/1282560/…

geometry data.stackexchange.com/mathoverflow/revision/1038474/1282557/… data.stackexchange.com/mathoverflow/revision/1038477/1282560/…

discrete-mathematics data.stackexchange.com/mathoverflow/revision/1038474/1282557/… data.stackexchange.com/mathoverflow/revision/1038477/1282560/…

Another tag which was deprecated (and eventually it was made synonym of an existing tag) is topology: data.stackexchange.com/mathoverflow/revision/1038474/1282557/… data.stackexchange.com/mathoverflow/revision/1038477/1282560/…