5:32 AM
The various stackexchange pages seem to recommend against blacklisting except in the following case: after burninating, the tag keeps reappearing. That is, it seems like we should try burninating first (even though the words themselves sound like burnination is more extreme).

0

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...

@S.Carnahan I have mentioned some examples from Stack Overflow where tags where existing tags were blacklisted.
You can find them here in chat:
Another part which I saved in chat is related to posts having only the blacklisted tag, but some further comments can be found there:
@YCor Since you've mentioned questions which only have single tags, I have posted the summary here in chat. However, I suggested blacklisting those tags mainly to prevent them from being added to new posts - I think this can be done without retagging the old posts. (Burnination would be a different matter - but nobody is going to actually suggest burnination or merging of those tags without major cleanup before that.) — Martin Sleziak Feb 1 at 1:11
I would recommend against burnination before the tag is sufficiently cleaned-up. That's why I think that blacklisting is a better option here.
In case it helps to clarify things, I will add link to proposal on Mathematics Meta by Asaf Karagila: Can we please have a “deprecated tag” feature? As it turns out, what he requested there can be done using blacklisting.
These are the example from SO:
Feb 27 '19 at 17:07, by Martin Sleziak
The examples I was able to to find are from Stack Overflow. From what I read on their meta, it seems that hidden-features and code-golf are blacklisted - although they still exist on some questions.
@S.Carnahan As you can see, I have posted something on meta: What to do with the synonyms for the blacklisted tags?
If you prefer to discuss this with other moderators first (if you prefer to create the post about this issue yourself), I do not have any problem if my post is deleted.
Of course, if you think it is worth reviving that discussion, you're more than welcome to explain the objections to blacklisting those tag in an answer to the older question: The existing deprecated tags should be blacklisted. (Nobody posted the answer there when I posted it.)

5 hours later…
10:30 AM
Should also the question whether those tags should be deprecated be discussed? Or this considered a consensus of the MO community?
I think that the decision that those tags should be deprecated was before my time on MO. (Or at least I wasn't really following meta/tea discussion back then.)
Jun 16 '17 at 15:19, by François G. Dorais
@MartinSleziak: These tags have been deprecated for a very, very long time. I don't remember the specific discussion where they were deprecated. Some relevant tea discussions are in the very long "tag merger/rename requests" thread: http://tea.mathoverflow.net/discussion/34/5/tag-mergerename-requests/
You'll need to use one of the mirrors instead of the above link - since tea archive seems to be down.
Or simply download the tea archive which was created by Scott Morrison.

2 hours later…
12:09 PM
Removed tags (from the most recent ones): main, meta. main, meta.

@MartinSleziak this meta thread seems to contain much of the relevant history.

I see that is mentioned there in a comment:
On a different note, if you are looking for tags which invite problematic questions, look no further than the deprecated tag 'geometry', which is much larger than 'calculus'. — Ricardo Andrade Aug 18 '13 at 23:50

For instance, several tags which are typical names of courses in the US system: calculus, abstract algebra, linear algebra, were discussed, resulting in three outcomes. (Which I agree in keeping linear-algebra which is a relevant theme, while eliminating calculus which doesn't exist as mathematical subject, and abstract algebra as research-related subject)
E.g. from a research-perspective point of view it's just absurd to call group theory "abstract algebra" but seems to reflect the educational system at some places. Algebra being abstraction, abstract-algebra makes little sense by the way, although some books in English language with such a title exist. It seems for some people to make, at an educational level a distinction with linear algebra, whence the unfortunate adjective.
At the opposite 'geometry' is a fashionable research subject tag, for instance there exist a lot of conferences with a name such as "geometry 2020" or "geometry in some place". But it's overly broad, and resulted in an incoherent tag which was duly deprecated (at that time — [this above-linked thread from Aug. 2013— I was already active on MO but not on meta or retagging).

12:39 PM
Is some of the discussion you mentioned in answers which are now deleted? (That would explain why I don't see it.)

1 hour later…
2:02 PM
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MathOverflow has a few problematic tags which are not inappropriate by themselves but suggest off-topic ideas. A prime example of this is the calculus tag. Sometimes a research-level mathematics question does involve some calculus so it is not inappropriate to tag such questions in this way. Howe...

It doesn't seem to be deleted, does it?

No the question isn't deleted.
But you have mentioned above some discussion of abstract algebra in that thread - which I do not see.

2:32 PM
It seems that this particular question has several deleted answerws. In fact, 21 of them.

3:03 PM
Overlaying two domino-like constructions such that all individual pairs of domino-like cells in the overlay have matching symbols - this question has a deprecated tag and it has recently been bumped (edit to the answer). I am not sure which tags to use, perhaps and seem reasonable.
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Imagine I have two $n$ x $m$ assemblies of $P = (n*m)$ unit square cells on the plane, $(c_{(a,1)}, ..., c_{(a,P)}) \in A$ and $(c_{(b,1)}, ..., c_{(b,P)}) \in B$, where every cell, $c_k$, in a particular assembly must have a distinct color/value. Here, $c_{(a,i)} \neq c_{(a,j)}$ & $c_{(b,i)} \n... 23 hours ago, by S. Carnahan I see two advantages to the current situation with the synonyms: (1) No new uses of the old tag, and automatic retagging on edit. (2) We can still search out the tag by hand (e.g., using a browser's "find" function on a page full of questions) and manually change them over time. The idea with Ctrl+F perhaps works for and for ; but not really for , since it is a substring of . (Or maybe you have to search in a more clever way than I did.) @MartinSleziak oh I hadn't double checked, I thought it also addressed "abstract-algebra". 2 hours later… 5:08 PM @MartinSleziak This question has been retagged. I have also marked this in the list of questions with deprecated tags. 1 Imagine I have two$n$x$m$assemblies of$P = (n*m)$unit square cells on the plane,$(c_{(a,1)}, ..., c_{(a,P)}) \in A$and$(c_{(b,1)}, ..., c_{(b,P)}) \in B$, where every cell,$c_k$, in a particular assembly must have a distinct color/value. Here,$c_{(a,i)} \neq c_{(a,j)}$&$c_{(b,i)} \n...

5:30 PM
The link ""Indra's Pearls: The Vision of Felix Klein"" is broken - it is in this answer: Are there other nice math books close to the style of Tristan Needham? However, as the post contains the full title, the link is not that essential.