A question that's not exactly rhetorical but the answer IS implied.
for example; "am I annoying you?"
you're meant to say no, and they are aware that they are indeed annoying you.
It's still a rhetorical question, but of a particular subtype.
While the reference notes that "in all cases, the rhetorical question is asked for the purposes of making a point rather than to obtain information," your rhetorical question is of subtype rhetorical-point.
I don't believe that this is a grammatical thing; it's more social I suppose. When you ask somebody if you are annoying them it is not supposed to be because you know that you are already and they are not supposed to just say "no". When I ask somebody if I am annoying them, it is because I feel it is likely that I am annoying them — only they are too polite to say so. I don't want to annoy anybody and I certainly don't want anybody to have to sit there and endure me out of politeness. Therefore, when I ask if I am being annoying I am looking for a honest answer because I'm not certain if I am and I do not wish to be.
If someone is being annoying, knows they are and asks if they're being annoying expecting to be told "no", well they're just being fake; to themselves as well as the other person involved. So, basically, the question isn't really supposed to be rhetorical at all — it's just supposed to be a question.