What makes a question rhetorical?
Solution 1:
Is there a term for questions which are really instructions?
Those of us who are married will be familiar with the less than rhetorical - "are you planning on going out looking like that?" or "do you want a plate?" as we drop crumbs everywhere.
I'm not sure the "have you considered accepting an answer" is really an instruction, but more a request posed as a question.
Solution 2:
As defined by the NOAD, a question is rhetorical when it is "asked in order to produce an effect or to make a statement rather than to elicit information." (See also the Oxford Living Dictionaries.)
Have you considered accepting an answer or starting a bounty for this question?
The question is rhetoric because it is not asked to get an answer ("yes, I did consider both options"), but to remind the users they should accept an answer, or to offer a bounty if none of the given answers satisfy them.
Have you decided where you are going on vacation?
The question is rhetoric if, for example, the purpose of the question is to remind those who read/listen that they are supposed to report in which days they will be away on vacation.
In both cases, whoever asks the question is not interested in an answer, but wants to remind somebody else of something they should, or could do.
Solution 3:
I rely on "Farnsworth's Classical English Rhetoric" for all rhetorical matters, and he writes that "Usually a rhetorical question implies its own answer. In other cases the speaker expects that no good answer is possible, or wants to make a statement indirectly by burying the question's premise." He covers 14 pages with explanation and examples of the various types of rhetorical questions, formally called erotema.
https://mannerofspeaking.org/2012/03/28/rhetorical-devices-erotema/ gives the definition of erotema as "A question that is asked without expecting an answer because the answer is strongly implied; a rhetorical question."
Rhetorical questions are used for rhetorical effect. So if someone is asked if they would like a new car free of charge they might reply "Is the Pope a Catholic?" and that question is rhetorical because it needs no answer because both people know the Pope is Catholic, so the implied answer "Yes" doesn't need to be spoken, and the implied "Yes" is more emphatic than the spoken "Yes" would have been, because it makes the other person think of the answer themselves, rather than just hearing it.
I was taught that to be a rhetorical question the answer must be something that most people would be expected to know, so the "Is the Pope Catholic?" reply, as given above, would be a rhetorical question because it implies the answer "Yes" and everyone would be aware of that, but, even if the questioner didn't want an answer, had the person above replied with the question "Is my Aunt Gemima's birthday on the third of January?" that would not be a rhetorical question because most people would not know the answer, and neither "Yes" nor "No" is implied.
To sum up, a rhetorical question needs to have a rhetorical purpose, normally to make a person automatically think of a particular answer, rather than telling them the answer.