"Diversity" in RP is a tricky thing, in my opinion. At the risk of infuriating someone, it's almost laughably easy to tell when a man is trying to roleplay a woman and vice versa. At least, that is my experience, but then I am someone who is highly observant and intuitive about behaviors and subtleties that many others miss. I have roleplayed male characters, and while I'd like to think I've done a decent job at it, I would never sit here and say that I can portray a man as well as an actual man could, because I am not, and never will be, a man. And no, I'm not interested in gender politics, I'm simply giving my own opinion here. 

I think that people give their best RP performances *by far* when they stick to what they know. That doesn't mean you could never *convincingly* portray another race/gender/etc, but I don't want convincing quality RP, I want mind-blowing. Whenever possible, anyway. I don't think it's necessarily brave or edgy or courageous or what-have-you to leap far out of your comfort zone and believe that you can jump into the mind of a character whose shoes you've never even thought about, let alone walked in. That smacks of arrogance to me. I could give some examples, but I don't want to further risk ruffling feathers.