This is from THE CODE:
"34. Feinting with the body. A player may feint with the body while the ball
is in play. A player may change position at any time, including while the server
is tossing the ball. Any movement or sound that is made solely to distract
an opponent, including, but not limited to, waving the arms or racket or
stamping the feet, is not allowed."
Thus, moving during the service is allowed, even IF one of the purposes is to distract the opponent. The only time it is NOT allowed is IF the purpose is SOLELY to distract the opponent.
I love it when guys try to call a hindrance on me for moving during the serve, I tell them to just pay attention to the ball, i can move whenever I want. Of course, I am not waiving my arms or stomping my feet, I am simply changing position, moving from one side of the non-service box to another, or moving towards the net.
If the purpose of the move is to distract the server, then it is a hiderance.... but of course that is a subjective decision.
I played a match where everytime I tossed my serve the "up-man" would start shuffling his feet (causing squeaking). I tossed and caught a couple of times, each time he would "squeak" just as I tossed. Finally I served and hit the up man. I told him I was sorry, but I was distracted by a squeaking noise coming from "somewhere". Then I called the score (taking the point) and moved to the other side. The look on his face as priceless and the mysterious squeaking never returned.