but I am concerned about starting a feedback pissing contest. I have 100% positive feedback now, and want to keep it that way. So is the satisfaction of sending such nasty feedback worth the risk to my own unblemished position, should he care to respond?

Wait, you're telling me that...

- Ebay has a feedback system designed to inform others of scam artists, but...

- the same system allows the scam artists to damage your reputation even though they haven't purchased anything from you, and...

- therefore fear of retribution keeps the system from working?