As to "not playing those underhanded games", that's probably the best idea you've had all day. Sounds like a deal worth avoiding with a seller worth avoiding.
If you're really chapped about losing the deal (I wouldn't be, see above), then put the entire chronology of the deal - including the pms, showing everything - up in a post on the sale thread, or on a thread you control with no comment of your own. Just "this is what happened". As the old saying goes "sunlight is the best disinfectant".
I haven't had any issues on this site but, like with anything else, there's a first time for everything.
