I've lurked here for a while but never posted, but I was in a guild group the other night doing 5-mans when this question was raised.
After thinking about it, my speculation was thus:
THE BASIC CONCEPT is that someone or something that has existed within Azeroth that WE CAME INTO CONTACT WITH left this "impression" upon our player-character, affecting us in some subtle, undetected way.
We were killed by Arthas - with a weapon of the Maw no less (Frostmourne).
Sadly I don't really have much to elaborate on that point at the moment, I just wanted to raise the idea here because I hadn't seen any threads about it yet.
Arthas killed Sylvanas and rezzed her with this power, and killed us later on at the climax of Icecrown Citadel. He attempted to do the same thing to us but was interrupted.
I know I'm crazy, but...could there be more to this?