AbigailII: In the current version, I agree it would be nice to see where you have guessed at - but not 100% needed since you can see it in the move list. (which a long term request is to make all games be able to be played without having the move list on - but I've given up on that request.)
Anyway, yes - if the guess would be hidden from your opponent, there has to be a way to show you where you guessed at yourself... even though I see Fencer solution would be just hide the wrong guess ? from the move list from your opponent - but would be nice to have it shown on the board.
By hiding the guess from your opponent I think will stop many of the people making "safe" moves - probable not all, but I think it would help out a lot.