I'm thinking of something that allows characters of level 20 plus to log feedback about other characters, which the imms can then refer to if they want. I'm thinking:

Feedback gargoroth + good rp while we ranked.
Feedback gargoroth - whined when I killed him and took one item.
Feedback gargoroth - for some reason, didn't attempt to defend inner when I raided solo
Feedback gargoroth + I'm a newbie and this guy took the time to help me learn to regear.

Each entry would be stamped with ip address and char name. Imms could use a command to list all positive or alternatively all negative feedback. This would allow them to better assess whether someone only rp's when they know their imm is likely around, is a regular griefer or someone doing a highly targeted looting for a reason, or whether their rp improves the experience for other players even though an imm has yet to snoop it.