I don't see it as right to call them arseholes (or assholes for that matter.) Indispensable part of the human anatomy, shouldn't be disparaged in that way.

Anonymity - nothing wrong with that, and the easiest thing to achieve. There are occasions when it makes sense too. But sticking a one-off label after the GUEST (like Wilda Beest for example) doesn't in any way reduce anonymity, it just makes it easier keeping track in a discussion, and is thus a courteous thing to do. Wearing masks and fancy dress at a party could be fun, but it's better if different people wear different masks and different costumes.