Feature Wishing Well, Bugs and Problems, The Parlor Room, Writing Workshop, Advanced Editor, Newbie Central all have something to do with the site. Apart from Alex there isn't any current way of moderating PM's to see if they were about the site or not, and if there was it wouldn't really be a Private Message, would it?
I just don't think it should bring any bragging rights. And we don't really need to see how many PM's somebody has sent. Forum posts indicate contribution. I get your point of view about the PM's, but we really don't need it, and it doesn't show your contribution to the site. If it did people like primates could start flooding everybody's inbox with junk mail (remember the Sethaniel incident), and getting his PM's up, and there'd be no right way of proving it wrong.
SOOO DANM TIRED OF THIS DANM ARGUMENT!!!! WE DONT NEEEED ANYTHING!