To be a successful trader you must know the rules of the game. You must also know if information about you is "leaking" to your likely counterparty (i.e. the specialist). I know the specialist is able to identify YOU as a retail trader and knows which broker you are trading with, and can minimally get a good hunch "it is you again" if you trade the same stock frequently. What else does he know or not know? E.g. is he able to tell 2 customers apart from the same brokerage, or not?