The recipient of a PM can report the message to the admins if they feel (rightly or wrongly) that it violates the forum rules or otherwise requires attention from the admin. (Look in your inbox for the Report To Admin link on every message.) The report page includes a text field allowing additional information to be reported, including the reporter's own spin on the situation. If you sent a PM to OgNasty expressing your hostility towards him and theymos, he is naturally going to report it and theymos is going to read it. This is a standard moderation tool and requires no conspiracy on the part of the administration to tamper with PMs.