I personally would like to know what religious background someone is coming from. There was a case of someone a couple months ago making posts seemingly trying to get people to convert to his faith (Jansenism, was it?) and didn’t list a religious affiliation. When I tried to ask about it, people complained that I was being nosy.
Gender should be optional. I’ve been more open about mine here than I normally am on forums. As someone else said, female posters on the Internet generally are often treated differently and presumed to be interested in different things. I have had situations where other female posters just assumed I would be interested in “girly” chat in PMs or worse yet was on the make for some guy associated with a forum, despite my being old and married (apparently those things don’t slow down some “operators”). I have less than zero interest in either thing and come to forums to discuss the topic at hand and no intepersonal drama.