I have an ongoing game with a skilled player. Early the other morning, after an all-nighter at work, I settled down at home to play chess. I noticed a good line that would win a pawn, and started typing notes on my intended attack. After further staring at the board, I noticed a slightly better approach, and just before clicking Move, I erased the old line to retype it. That's when I noticed that I was typing in the Message Your Opponent text field, and nearly sent my plan to the opposition.
Now that we have a handy note area, perhaps you need a little warning are you sure you want to send this message to your opponent? window for the very, very sleepy.
Heh, heh, heh. (:-}