I just heard about the cable-pulling hack in another MMO last week. Apparently it is a big problem in many games right now. And with UDP packets, a crash vs pulling the cable are the same thing to the server... the client simply stops sending data. A /quit could behave differently, as it sends a final disconnect message to the server... but then you still have those, like vannaka mentioned, who simply /quit to avoid dying.
May I ask if there is a time-out for the current implemented work-around? If you were training armor for instance, will the server time-out the combat in a set amount of time... or can you get stuck like this until someone else comes along and kills the creature/player you were in combat with?