@HarryGindi Sorry to be dim, but I looked at your favorites, and it's empty. I don't know how to look up your favorite tags; could you send me the URL for that, please? If you look under tags and enter sheaf-theory, you'll see it's there; it seems totally kosher.

@ToddTrimble He clearly means favorite tags, not favorite questions.

You can see questions in your favorite tags by searching for intags:mine.

But I doubt there is a way to see favorite tags of another user. (At least for regular users, maybe mods can see more.)

Still, the only case I can imagine what Harry Gindi describes only if some tag has been merged to tag-removed by a moderator.

If that's the case, this sounds like question for François G. Dorais. (I might be wrong, but my impression is that he most often deals with tag synonyms and tag management. So he might remember which tags have been changed in this way recently.)

The only recent tag removal which I remember mentioned somewhere was open-problems-list; see here: chat.stackexchange.com/rooms/10243/conversation/… But I assume it was merged with open-problems and not tag-removed.

@HarryGindi Do you happen to remember whether you had open-problems-list among your favorite tags? (This tag no longer exists.)

If I can think of some another tag that was removed, I will let you know. But as I mentioned above, François G. Dorais is probably the right person to ask. (Maybe Todd Trimble can confirm whether it is true that from the moderators team, François is the one who most often deals with tag-synonyms/tag-management.)

meh it's not worth it. I was just curious is all!

"it's not worth it", "let it all go down the drain", "not moving a finger any more"

Although I am pretty sure that sometimes I thought (or maybe even wrote) something similar when I got frustrated from some discussions on chat on meta or from some close/reopen wars and arguments about them, etc. (Although in my case, mostly on another site, not on MO.)

@MartinSleziak I was inactive for about five years. I don't think it's worth the effort if it's even possible

I was just curious which tag I liked enough to add as a favorite but was bad enough to get binned while I was gone =]

Yes, I agree that it is more of a curiosity than actual question.

I thought it might be a recent change. (At least originally I understood your inquiry as something you notice only recently, so I thought that it is a tag removed recently.)

Very glad that simplicial stuff is still around, though! I think that one was a tag I started.

At the example with open-problems-list tag shows, users not always agree with moderators' actions about tags. So if some tag was removed and some users think that that tag was useful, that might also be useful information for the mods.

I think I learned from my first ride on the MO merry-go-round that it's not worth it getting involved in arguments over moderation and administration here.

"Who voted me down? Answer me you coward!!"

There are still a few meta.MO threads from back then that I remember fondly, namely the ones involving Ian Durham, haha. Does Pete L. Clark still post all the time?

That was the only time we ever teamed up for the greater good, as it were.

On math.SE I see some answers in October. On MO there is answer in September and other activity - comments/edits - more recently.

If you meant whether Pete L. Clark is active on meta, there is no activity for a long time neither on Mathematics Meta nor in Meta Mathoverflow. (I remember that Pete L. Clark explicitly mentioned in some discussion on Mathematics Meta, that he wants to end his participation in meta and only be active on the main site.)

@ToddTrimble By the way, when I was at that conference in September, I was speaking with Amar Hadzihasanovic, and he said he was working with those Steiner complexes but with modified morphisms. I had him take a look at your notes on tetracategories, and he was curious why you needed to use associahedra rather than simplices to encode the associativity coherences.

I remembered reading somewhere that associahedra are related to biased versions of the associative law and simplices gave an unbiased version, but I don't remember the reference.

Was there a reason why you had to use associahedra instead of some other more regular polytope?

@HarryGindi It's pretty clear that I was just continuing the sequence categories, bicategories, tricategories, which in terms of pasting diagrams uses associahedra, not simplices. So there's basically your answer. Of course, the first barycentric subdivision of the associahedra has a nice simplicial description... one should see what that might mean for bicategories and tricategories and continue...

Thanks!