The question Understanding risks of logging into Stack Exchange sites from a shared computer or network has two tags which have only been used once and have no tag excerpt or wiki: and . According to What causes a question to be tagged as [untagged]? that means they should be deleted after six months:

Tags that only exist on one question are automatically removed after 6 months, unless the tag has a tag wiki.

They should have been removed somewhere halfway 2019. Yet, the tags still exist.

Looking at the revision history, they've been removed by a ♦ moderator (which presumably deleted the tags about 24 hours later) but that edit was rolled back after a week. My gut feeling says this somehow blocks the automatic pruning of these tags, but I could be wrong since of course I have no way of looking at the source code.

I've checked Why wasn't this tag removed - despite having single occurrence? but that seems to be a different case; the tag there has an empty tag wiki and excerpt: https://mathoverflow.net/posts/295234/revisions and https://mathoverflow.net/posts/295235/revisions. Those IDs can be found with this SEDE query, and the corresponding query for and comes up empty.

  • At the moment, the tags are still in use. By that single question. Hence no removal of the tags, right? If you want the tags removed, remove them from the question (I just replaced them with a more useful tag) and wait till they're roomba'd, but they won't be roomba'd while they're in use. Am I misunderstanding the situation?
    – Mast
    Commented Nov 20, 2019 at 9:04
  • 2
    Tags that only exist on one question are automatically removed after 6 months, unless the tag has a tag wiki. I think it's better to leave that question in its former state, in order not to obstruct the analysis.
    – Glorfindel Mod
    Commented Nov 20, 2019 at 9:07
  • Ah, that part. Yes, I'm not sure why that didn't happen so that looks like a bug indeed. Note: considering the only people who can answer this are the developers and I'd already made the edit, I don't think your rollback is going to help with the analysis.
    – Mast
    Commented Nov 20, 2019 at 9:10
  • 2
    You sure that there are no rejected edit proposals for the tag wiki? Commented Nov 20, 2019 at 9:36
  • 1
    @Sonic doesn't look like it, according to some SEDE queries which I have added to the question.
    – Glorfindel Mod
    Commented Nov 20, 2019 at 10:35
  • Probably (also can't see the source code) vaguely related to this: meta.stackexchange.com/q/213474/282094 SBD.
    – Rob
    Commented Nov 20, 2019 at 10:45
  • Thank you for the question. Could you please tell me if you have any other examples of this behaviour? It seems that the tags you mentioned are gone, so I cannot look at what has happened. Commented Jan 7, 2020 at 13:44
  • @NicolasChabanovsky I fear a user who was trying to be helpful accidentally spoiled this example. I'll have a look if I can dig up more of them via SEDE.
    – Glorfindel Mod
    Commented Jan 7, 2020 at 13:47
  • @Glorfindel That would be very helpful! Thank you! Commented Jan 7, 2020 at 13:49
  • @NicolasChabanovsky here is a list of tags which should be pruned, but aren't. I'm not sure I'm able to find a similar example (with the rollback) as in this question, though.
    – Glorfindel Mod
    Commented Jan 8, 2020 at 13:41
  • @Glorfindel Thank you! It's very useful. Let me investigate the issue a bit more. Commented Jan 8, 2020 at 13:49

1 Answer 1


It turns out that there are two different thresholds one for main sites (6 months) and another for metas including MSE (12 months). We run a script once per month which means in some cases the period might happen to be almost 7 and 13 months respectively.

The fact that the edits were rolled back is entirely incidental.


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