I am not sure whether questions about $F_\sigma$, $G_\delta$ sets and similar stuff should automatically be tagged descriptive-set-theory.

There are many tag edits in the revision history of this post:

This tag was added there by t.b. and later removed by Arthur Fischer. (Both of them are users whose opinion about tagging should certainly matter.)

Probably the answer to the above question is - it depends.

I don't feel that descriptive-set-theory fits, which is why I didn't add it back. IMHO DST is more about regularity properties of "definable" sets in Polish spaces, whereas asking for examples of Borel sets (of some prescribed complexity) feels simply topological.

I think Asaf and I have discussed this before (even in this room but I'm too lazy to search).

It seems that I should have read revision history more carefully.

@ArthurFischer I am not sure I recall Asaf talking in this chatroom at all.

I cannot find anything by Asaf. The same search for messages posted by me or you returns at least some results.

(I am not sure whether it is possible to search for all messages posted by some user in a room. But I at least tried to use some simple word which I suspected would have appeared.)

In any case, dst was mentioned in our discussion here:

In fact, here are all your chat messages in chat containing the word descriptive: chat.stackexchange.com/search?q=descriptive&User=34511

(Assuming the search in chat works as it should.)

@ArthurFischer Since you peeked into this room, I will ask you about subspaces, too. I have mentioned this tag in Mod's Office: chat.stackexchange.com/transcript/20352/2015/9/28

Just knowing that you saw that message would be enough. But if you let me know whether I should start retagging questions having this tag, it would be even better.

But since I have asked there, we should probably continue the discussion in the other room. (Ping for just to get your attention to the issue. And since this room has already been bumped, I pinged you here rather than over there.)