I'm sure this topic has been covered at length a thousand times already, but since it just happened to me, I want to throw down my two cents.
If you want to steal from me all of the uber 1337 l00t that I earned through role-play, fine, have at it. All of my characters are disposable, especially on this server, and that goes triple for their items.
All I ask in return is that you give me back what I put into getting those items, namely, a somewhat enjoyable experience. You want my sword? Beat me senseless and take it from my bloody hand, or better yet, challenge me to a duel and knock it from my hand, or better still, get me stupid drunk and win it from me in a bet.
For crying out loud, if you're going to yank something from my bag while I'm in the fugue plane, don't take my main weapon, especially if you're in my own party and it's clear that I'm not permadead. Don't take something from me that I can't replace. I don't know if that counts as griefing, but it feels like it on my end.
I play plenty of evil characters, and I loot plenty of dead PCs. However, when I go rifling through a level 7 Seeker's belongings, I might drool over their hyperpowered loot, but I absolutely don't touch it. I'll help myself to a small sample of their potions, minor wands, or other disposables, but I leave their quest rewards alone.
I don't touch that stuff because I know how much time and effort they put into their characters, and if I've just got my hand in their bag while they're dead and can't even so much as make a reflex save, I didn't earn the right to take it.
I'm going to extend that level of respect to every player I encounter. Please show the same respect to me.