If he keeps flaking out on potential buyers, can you pull his ad???
If he's not serious about selling it and posts it, then it shouldn't be posted...
Comments are not allowed in for sale ads... But a false ad is basically a "comment thread" and then comments should be allowed in that thread to warn potential people what they are walking into, or pull the ad all together and save everyone the hassle...
If he's got interested buyers trying to coordinate shipping through a shipping company and then drops out, that is not fair to the people interested in buying the car... It's a waste of people's time... Is that fair to do to forum members???