Talking during a game is just rude. No proper player does that over the board so why it is an option online I have no idea. If I really want to say 'gg' to someone or even break out my creativity and form a sentence after a game then I have it wthin my skill set to navigate to their notes page and post there.
I don't want to wish my opponent good luck or have him wish me good luck before a game. We're playing chess, not roulette, why would anyone be wishing someone luck for a game of chess?
If people choose to not ask for a rematch because I disable chat then that is all the more reason for doing so. We played a game, now move along, we're not getting married, just play someone else next!
I wonder how many people who've disabled chat will come here to read this thread...