We used to train players who pissed us off. In everquest creatures had a tendency to switch who they were attacking pretty easily. So you just anger a bunch and dump them on the offending player. They call it "training" because you have a train of creatures chasing you.

Training generally wasn't punished because it happened a lot on accident.

were different rulesets in play(who could attack who, what could be gained in the process(money or gear), pvp was really an afterthought for them.

I can say though that in persistent worlds there is always a history, usually fresh "meat" too though.