When, if ever, is it appropriate to add the homework tag to a question that has not been acknowledged by the OP to be homework?
My position is that it is never appropriate, full stop. It’s fine to ask whether a question is homework and suggest the tag; after all, a newcomer may well not be aware that it exists. But to add it without asking is to claim the ability to read the OP’s mind, and that seems to me highly improper, even when it’s perfectly obvious that the question is very likely to be homework. (And I have been fooled a few times.) I have routinely rejected proposed tag edits of this type for just this reason and not thought twice about it. However, I recently got into an editing war with another experienced user who sees adding the homework tag to probable homework as being on all fours with adding a subject tag and wanted the homework filter to catch that question, since it very likely is homework. I see a very significant difference: I know whether a question is general-topology, say, but without a statement by the OP I cannot be certain that a question is homework.
I didn’t see it at the time, but not quite a year ago the same question was asked in a slightly different context, and the only answer said in part:
I and many other users consider it inappropriate to tag another user's question as homework unless they have explicitly said it is homework.
It received $10$ upvotes and one downvote. This answer to a much older question is in the same vein; it has $26$ upvotes and two downvotes.
I’m now curious as to whether sentiment has changed. I’ve no real reason to think so, but the discussion got sufficiently heated that it seemed a good idea to open it up here.
(Oh, and feel free to add or change tags: I don’t follow Meta closely enough to be very familiar with the tags.)