I recommended deletion in review of a submission with the reason corresponding to "not an answer" (NAA) on this Q&A: What does $H\parallel ab$ mean?
This was in the "low quality posts" review queue. At least one person appears to have agreed with me, and, since it was in the review queue, I think someone before that must have flagged it.
Rob came after an added a comment, "While this post may be unsourced speculation, it is an answer to the question."
This to me is an interesting corner case. The question itself, in this case, has already been closed for lack of enough information to formulate a proper answer. Before that happened, we got the "answer" at issue, which is pretty much pure speculation as the terms have not been defined. There is some technical sense in which I agree that Rob is correct, but I question whether it's a meaningful sense in the case here. When I reviewed it, I was thinking more along the lines that there is no answer to this question because the symbols aren't defined, so anything here is NAA.
Do we really think that it's ok for any user who comes along to guess what the symbols meant here and speculate on an answer? I don't think that's what we want. Is there a different flag or category that would have been more appropriate in this case?
For contrast, I think the situation would have been different if the question had been well-formed with the terms defined. The problem here, in my opinion, is the interplay between the poorly written question and the speculative answer.
The canonical mother-meta post on the NAA flag seems to be this one: How do I properly use the "Not an Answer" flag?
Here is an earlier discussion on the NAA flag in context of Physics SE: Are we clear on what the "not an answer" flag is for?
Both of these seem to cover the primary cases, but I still think the case raised here is different and probably rarer.