I would have thought we would welcome them to defend, or to clear up, anything? I mean, if someone has bought a fake, and the usual 'contacting the seller' process has failed, there isn't really a leg to stand on. Perhaps threads could take the form of the coin itself being the title, and the details in the opening post, not accusing, but asking opinion? The the seller could be contacted, by the buyer, and given a link. Keep it open and honest.. and properly moderated.