Touching the stones too much
Kungfu: While visiting a certain local Go club, there was a man playing a game of go. He had the annoying habit of playing a stone, and then touching around 5 to 7 stones nearby to "adjust them". I can understand and accept the need to fix the position of the occasional stone, however, this was excessive enough to be annoying. Please don't do this in real life.
Alex Weldon: Please feel free to touch the stones on your computer screen all you want. ;-)
phenomene: Dear opponent, if you don't want me to adjust the stones too much, please put them in the right place to begin with. :-) Yes, I have this bad habit, but some players never put their stones on the right point. After a while, the position becomes unreadable.
victim: Actually, I heard that putting your stones slightly off-centre instead of aligning them as if you had used a ruler is considered good style in Japan. This is probably related to regarding crooked trees as prettier than straight ones, as practiced in Japanese gardening and the art of bonsai.
Jim Kiraly: I once played an opponent who would slide his stones into position as if playing shuffle board. Just kind of push them, unguided, two or three space across the board whenever making a move. As long as the stone was relatively close to position it was intended for, he would just leave it. More often than not I would have to ask him where the stone was meant to be played and place it there for him. I'd much prefer to play a stone toucher, than a stone slider! :-)
Dansc: Sounds like a cool way to play the stones, if done so that the stones always end up where they should. I'll have to start practising :)
AlakofKGS: Barring the case when the stones are on a completely different point than they are supposed to be, there is a very good reason to not readjust the stones, and that is because it helps you practice seeing the position in your head instead of on the board. It can sound difficult at first but it is really worth it (like doing math in your head vs on a calculator -_-). You should thank your opponent for playing messily!
SamMadHands?: I thought you were supposed to hold the stone between the top of your forefinger and the pad of your middle finger and sort of thwack it into the board. Good resonance with hollow under board.