Does a rhetorical question (in text) require a question mark?
A very good, and perceptive, question. Sometimes a rhetorical question does , and sometimes does not, require a question mark. You might hear a woman remark about a cute little two-year-old "Isn't she darling." The phrase is a grammaticl [syntactic] question, but it's in fact an exclamation, and as such requires an exclamation mark.
If I were you, I'd simply avoid avoid them, if possible.