Screen readers have already been mentioned. But also, how about people from cultures that don't play chess? How about people from cultures that do play chess that just haven't ever given time to the game?

I learned to play chess when I was a kid, but never had anyone to play with. The internet wasn't any help, either, because when you're a kid it's just not that much fun to constantly have your ass handed to you in a game. I gravitated to other games as a result. And now this thing just gives me that same sense of dread, of "I have no idea what the hell I'm doing", even though I know all of the rules of the game, because I'm so not involved in the culture of the game at all.

Congrats, you've alienated several classes of users.