I haven't seen anything represented in a flag yet that I didn't already know through posting (aside from locations). I don't think simply knowing that someone is a Christian, or a lesbian, or an atheist, or whatever, is really an issue. Those are all things that come up in conversation here regularly.
As far as I'm aware, stating your political leanings is forbidden, period. At least one poster was banned for having a political signature during the last presidential election (I believe it was either a donkey or an elephant, but I didn't see it myself). It's not a risk I would take. Even when it's relevant somehow, most posters just say Party A and Party B or something.