I've heard some disturbing news about sertain player Customizations. I don't mind if a player wants to modify their own client so that appearances change so much to them. (sound enhansements or even making dragons invisible and such)
But I recently caught wind of one paricular that allows you to change the size of allmost any object in the game including your charactor. I would have been ok with this accept for the fact that I also heard whatever size the client sees is also the size that the server sees. This allows the player to become big enough to not drown in the sea, or small enough to be able to pass through openings that they should not be able to. This makes Kutit form obsolete and in my opinion creates a possible disruption of emersion in the game for players that would rather not hack their client.