One of the things that attracted me to forum boards (and IRC channels in the early days) is the anonymity of the systems and the fact that everyone is truly equal (until they open their mouths) and there's no preconceptions or prejudices that occur everyday in real life. For me it opened up a whole new world, and in that world there were no men or women, no young or old, no fat or thin and no black, coloured or white.
I understand that lack of identity goes against that which is human in us and therefore the need for avatars and signatures. Now we all know that the other members of a forum are as likely to choose an avatar or signature that decoys us from seeing them as much as they might be choosing one that truthfully represents them. With this in mind I've always been interested just how much people's impressions of other forum members are swayed by the avatar or signature of that member. I like to think I'm pretty good at taking people as being purely the sum or their posts and not being drawn in to treating or talking to them differently because of their avatar or sig. I like to change my av and sig on a regular basis to encourage others to treat me the same way in return but I strongly suspect that the tone of replies people make to your posts and even the number of replies as well as peoples generosity with the thanks button can be affected by the 100x100 pixel image you choose to portray yourself by.
I'd be interested to hear any thoughts on this.