The rationale is that no one can police thought, and that disallowing OOC sources would open a floodgate. If you send something by accident to someone, and tell him to disregard it, and he then uses it... who is the say that your intended target didn't share it with him anyways? Are you going to report any such suspicion? The titans would then be forced to investigate every case? What if someone else used your message that you never sent it to? Was it from the legitimate target or the accidental recipient? Can that person be held accountable for information acquired accidently by a third party with no implication from himself? Besides, if a murderer mails the murder weapon to the police by accident, would the court really make the evidence inadmissible because it was only sent to them by error?
The burden lies upon the person that made the mistake. You can't OOC order other players to act a certain way, including ignoring the IC message you sent them.
