How to reveal the truth?

Is there anyway to let people know when a seller is blatently misleading people other than perhaps posting an thread in the forum? There was a Convergent audio SL1 Renaissance that had been for sale for a few days now, sold today. The seller posted the serial number but later removed it from the ad for unknown reasons. He said the unit was new and rated it a 10/10, then changed it to state it had only been used about 20 hours but still 10/10. I messaged him to get the serial number so I could call the manufacturer and found out some interesting facts. The pre was actually 5 years old not new as the seller described. I then called the dealer it was shipped to and they told me they used the pre for 5 years as a demo and show unit. They damaged the top and faceplate so they replaced those with new ones hence the newer designed faceplate on the unit now. They confirmed that they sold it to the customer about 3 months prior as a used demo unit. After finding out this information I still felt like it was a decent deal and made an offer to the seller, of course revealing the information just incase he didn't know for some crazy reason (seller didn't comment about the info). I felt like I was informed on what i was bidding on thought at this point while others would not know and would think they are actually buying a new unit. Anyways, do you guys know anyway through audiogon that you can inform people that this is whats happening so they can at least be informed about the product they are buying?