Is it rude to make questions about users?

Its REALLY rude,

But without them knowing or finding out

If they know about it beforehand and they say it's okay,and as long as the questions are not too personal it should be fine.If they don't know about the questions,then yes,it is kind of rude.

Not really, I tell you its perfectly fine! Except to just go to the right place to do it! c:

It depends. Though, it's better to just not make questions about other users.

Well I guess it just all depends

Depends on the question.

if it isn't insulting, inappropriate, or done with the wrong intentions/outcomes then i believe it is fine

I would say it is.

If you have a question about a specific user, just ask them privately rather than putting them on blast.