One thing I have done is removed the content of the private message.
We have a policy of not allowing the content of PM's be published on the site without the consent of the sender and receiver. That's why they are private messages.
Anybody who receives a PM they have a problem with (be it insulting or unfair) they can take it up with a mod. If it's a od involved, they can take it up with R.
A relitivly small issue, I know (sort of like turning the stove off while the house is burning down
) but it's a start