If I had a suggestion it would be to mandate the seller immediately post when payment is pending, to whom, and to post when their item is sold and again to whom. If the seller does not post in a timely fashion; responsibility falls on the buyer to post and the seller gets a strike. __ of strikes and you are banned from selling. Running the system this way will quickly out a seller trying to pull a fast one like what occurred in that infamous thread and they can be IP banned.
Either that or do nothing. Make it on the buyer to do their research on a seller. Before you fork over hard-earned money get a phone number, call the person, talk to them, meet in person, etc. If you get a bad vibe don't buy the item and warn the forum. If the item you want is across the country and has to be shipped the buyer has to ask themselves if they trust the person they potentially just met over the internet with $__ amount of money. If the answer is no then spend the extra cash and buy from a business where you can charge back your credit card and have other means of recourse if a scam occurs.
As someone who has bought countless things on forums I can safely say I have never sent any sum of money to a private party I wasn't prepared to lose.