I don't think that the issue here is so much that it is a matter of the preferences of the prophet, but more the triviality of this particular preference.
In some cases, "preferences" can be difficult to separate from beliefs and practices. So the sexual, political, or racial preferences of a prophet/theologian could be relevant here, when they have a significant impact on that prophet/theologian's belief system.
Thus, I think a better measuring stick in situations like this is the triviality of the question. Stack Exchange isn't a platform for collecting trivia, but rather for questions and answers that are of some actual use. See this related Q/A: Is it okay to ask about obscure, seemingly trivial Christian practices?
In this particular example, if the OP could demonstrate that this preference influenced Smith's religious beliefs or practices, that would be an improvement. Or, if he demonstrated that some Christian group would realistically seek to copy Smith's example in this area if they knew about his preferences, then that would make the question more useful. But as it is, I don't think this one escapes the "trivial" designation and thus is susceptible to downvotes and close votes.