I would agree with KY... it would be the classier, more gentlemanly way, to do it in private...
I believe the Boss here puts that in writing in the intro to the for sale section.
But if the OP'er who's posting the original For Sale , or Want to Buy ad is being a real dick about something after some private contact, I'd feel its fine if thats brought up, ..just to warn others who might be interested...looking out for each other,etc...
But if we go by the Rules as posted by Dave, it's a no no, though some have not abided them.
franc
