Conversation started Feb 27, 2019 at 17:05.
Feb 27, 2019 17:05
I will post here some examples showing that there are instances of tags which are blacklisted while they still exist. This is in connection with my post on meta: The existing deprecated tags should be blacklisted.
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.
In fact, in both cases the tag-wiki explicitly says the tag is currently blacklisted.
> This tag is blacklisted (see The mystery of hidden-features tag), use this search to list them all.
> Note: This tag is currently blacklisted and can no longer be used.
I found these tags here:
5
A: What tags are already supported by how-to-ask tag tips?

Shog9Right now? Just sql. There is guidance associated with a few other tags... But those tags are blacklisted - you can't submit the question if you use them. Currently on Stack Overflow, google, hidden-features and code-golf fall into that category.

There are posts on their meta showing examples what happens when somebody attempts to use such tag.
4
A: The mystery of hidden-features tag

Shog9You point out something I'd forgotten about: we never blacklisted this tag. I've remedied that: Given these questions cannot be edited, this serves to preserve the categorization of those in the archives while discouraging folks from posting new ones.

14
A: Burninate [code-golf]

Shog9The remaining questions are a part of Stack Overflow's history. Or mistagged. Either way, there's no particularly good reason for using this tag on any new questions, so like hidden-features before it this is now blacklisted:

Feb 27, 2019 17:52
In fact it is possible the the information about (hidden-features) was incorrect. We will see whether I get at least some answer here; Was the (hidden-features) tag “unblacklisted”?.
However, when I tried to put (code-golf) into the tag field, I got some warning. It looked like this:
Feb 27, 2019 18:11
This would be a possible explanation:
Blacklist items automatically expire if they are never triggered for some amount of time. It's possible no one tried to use it for too long. — animuson ♦ 1 min ago
We'll see whether we'll find out more details about that.
 
2 hours later…
Feb 27, 2019 20:28
0
A: Help cleanup tags!

Sam HopkinsI think it might make sense to make polytopes a synonym for convex-polytopes. Although non-convex polytopes are sometimes studied, convex ones are much more prevalent. Also there are only 36 questions tagged "polytopes" while there are hundreds tagged "convex polytopes."

 
11 hours later…
Feb 28, 2019 07:52
@MartinSleziak Just to save the tag-info somewhere in case the question (and together with it also the tag) gets deleted, here are the suggested edits from the previous incarnation: meta.mathoverflow.net/review/suggested-edits/301 and meta.mathoverflow.net/review/suggested-edits/300. And here are the recent ones: meta.mathoverflow.net/review/suggested-edits/449 and meta.mathoverflow.net/review/suggested-edits/448.
Since the question has been resolved, should it now be deleted? — LSpice 10 hours ago
 
12 hours later…
Feb 28, 2019 19:41
Looked this up. Blacklist items automatically expire if they aren't matched over a period of 90 days, and are at least 60 days old. Tags are excluded from this check, but the exclusion was not added until March of 2015. So we'd need to add it back in. — animuson ♦ 6 mins ago
 
11 hours later…
Mar 1, 2019 06:11
@MartinSleziak So it seems that this tag blacklist disappeared by mistake - now it is back.
3
A: Was the [hidden-features] tag "unblacklisted"?

Shog9Thanks for noticing! As animuson noted, we used to age away these tag blacklists. Which is annoying, because I had to re-type that whole message. That done, it's now back in black...list:

 
5 hours later…
Mar 1, 2019 11:25
Feb 11 at 17:27, by Martin Sleziak
A new tag was created. This does not sound like a good tagname to me.
Does somebody have a suggestion what to use instead of on this question: Convergence of Stochastic Flow but not Flow?
 
10 hours later…
Mar 1, 2019 21:16
0
A: Help cleanup tags!

Mike ShulmanThe tags locally-presentable-categories and presentable-categories should surely be synonyms. I would personally prefer that the former (much older, well-established, and less ambiguous, terminology) be the tag and the latter the synonym, but either direction of synonym would be better than havi...

 
9 hours later…
Mar 2, 2019 06:03
@MartinSleziak The tag-excerpt option only. Blacklisting is mostly useful for repeat offenders: deprecated tags that get created over and over again. That problem is very rare on MO. — François G. Dorais ♦ Feb 25 at 6:04
It seems the MO moderators dislike the idea of blacklisting deprecated tag while they still exist.
I have made a post on meta about this some time ago: The existing deprecated tags should be blacklisted. But I received basically no feedback there. (Although it gained some support - it is currently at score 14.)
14
Q: The existing deprecated tags should be blacklisted

Martin SleziakTL;DR: I suggest to blacklist the deprecated tags that still exist on some questions, in order to prevent them from being added to new questions. There are a few tags which are deprecated and should not be used at all, but still exist on the site.1 Ideally such tags should be completely removed,...

I will try once again to summarize what I see as a possible advantage. (Maybe this does not add too much to what I already said in that post.)
TL;DR: Blacklisting the deprecated tags would be an easy way to prevent these tags from being used in new questions. Even if there remain older questions in need retagging, at least the number of problematic questions would stop growing.
My main point is: Why should people do manually something which can be automated. (And retagging new posts with deprecated tags is a thing which has to be done regularly and users have to pay attention to it and check whether the tags appeared in new questions.)
I remember that when similar issue was discussed on Mathematics Meta (Can we please have a “deprecated tag” feature?), Asaf Karagila seemed relatively keen on something like that. However, he became moderator since then but I haven't seen this done with any tag on that site either.
(I do not know how often the moderator teams of the two sites discuss with each other, but you maybe talk about this with Asaf.)
The examples where this was done in practice are two tags on Stack Overflow I have mentioned above: chat.stackexchange.com/transcript/10243/2019/2/27 (Possibly there are other instances of this - but these are the ones I was able to find.)
Of course, all of this is probably irrelevant if the moderators think that the tag system on MO is already beyond saving and any efforts to do something with tags are just prolonging the agony.
xxxxx
The situation with the deprecated tags on MathOverflow - as I see it - is the following:
There are many questions with deprecated tags, the number of those questions is not decreasing too fast.
If you follow the links above you can find also how the number looked before. For example, there were 1000 questions with deprecated tags in August 2017. However, since August 2018 the change in the count of such questions was very small.
So if this trends remains, it might take rather long time until the deprecated tags get removed. In fact, it's possible that they will never be removed completely.
And I can easily imagine situation that the number of such question might be increasing if a few of the most active editors leave the site or become less active.
For example, during May 2018 the number of questions with deprecated tags actually increased.
Since there are (at the moment) only very few users who edit questions and pay attention to tags, if they did not have to pay attention to new questions with deprecated tags, they might be able to find better use of their time.
And whoever follows the tag edits on MathOverflow can see that there are some users who make an effort to remove the deprecated tag from new (or bumped) posts - although sometimes a post with a deprecated tag goes unnoticed.
Feb 23 at 23:01, by Martin Sleziak
SEDE returns 145 questions where the tag abstract-algebra was removed‌​, 713 questions for geometry and...
Feb 23 at 23:01, by Martin Sleziak
... 70 questions for discrete-mathematics.
The situation is diffent on Mathematics - there are enough users on that site who are willing to devote their time to improve tagging. For example, after it was decided that the (algebra) tag should be divided into (abstract-algebra) and (algebra-precalculus), enough users helped with this and the tag was removed relatively quickly.
in Tagging, Jun 20 '12 at 8:02, by Martin Sleziak
We went from 700 in October 2011 to 0 in February 2012.
As François G. Dorais pointed out in an older discussion, MathOverflow is a smaller site, so older questions cannot be edited so fast as on Mathematics. (Not to mention that some of the users object to almost all edits of old questions, or even to almost all edits.)
Feb 1 '14 at 22:16, by François G. Dorais
I agree with @quid. The MO turnover rate is much slower than MSE. For 165 edits, it would take up to two months to do without causing ruckus.
Still, I think that the difference between number of users willing to help with editing tags on MathOverflow and Mathematics can be clearly seen. (Of course, maybe I am biased - since I am more active on Mathematics.
The only instances where I have seen some larger tag being removed on MathOveflow were the tags merged by moderators into another tag and the tags removed manually by YCor. (I was involved in the removal of (proofs), but that was a tag only with 9 questions.)
Although I suppose that some more examples can be found before my time on MO (when Ricardo Andrade and quid were active in editing and tag-related issues).
Again, I'll just reiterate what I mentioned above: I do not really see the point of removing the deprecated tags from new questions when it can be easily automated.
Basically the only upside I could see in doing this manually is that when such an edit is made, other users who see the edit might be reminded that there are deprecated tags. (Although this post on meta shows that even if the edit summary explains why edit was made, users might still miss what the reason for the edit was.)
A very minor disadvantage is that somebody might think: "What? Questions about abstract algebra are not suitable here?" But this can be resolved by the text given in the warning. (And this problem is the same for all blacklisted tags - whether they are empty or they exist on some questions.)
xxxxx
@MartinSleziak The tag-excerpt option only. Blacklisting is mostly useful for repeat offenders: deprecated tags that get created over and over again. That problem is very rare on MO. — François G. Dorais ♦ Feb 25 at 6:04
BTW depending on the interpretation of the phrase repeat offenders from your comment, deprecated tag might qualify. (Although I will admit that it is a bit of a stretch and you meant it a bit differently.)
Certainly they have been used many times after they were deprecated - June 2017 for abstract-algebra, February 2016 for discrete-mathematics and June 2013 for geometry.
 
Conversation ended Mar 2, 2019 at 6:11.