I moderate another forum and we have done this, used to be 100 spam free posts now we have reduced it to 50, and it used to be a case of mods helping out with info etc if a dodgy deal was done but not now, personally i would name and shame as apart from removing confidence from buying within a forum it also helps destroy forum member trust, Times and forums have changed but this one seems a hell of a lot better than most...hopefully because of the unwritten respect for fellow bikers and i have always labored under the fact that you always try and help out a fellow biker if you can.
Your right Andy, it only takes a few bad members to kill trust..... hopefully we can avoid this on this forum.
Perhaps the seller had been misinformed on what years they fit. He/ She may to they're believe have been told that so had no problem in saying that to the buyer. If that is the case i would say sorry and give the buyer a full refund. Also, the seller may be embarrassed he/she sold the wrong part and is worried about any backlash. He/she may have spent the money and can not afford to pay it back yet. Or could be a compleat twat. I never name and shame as with forums way too many get involved that have no connection with the deal in the first place.