Well of course disputes are going to occur, hence why trading at your own risk is advised.
IMHO if you as the seller don't do your home work on who your buyer is and what their trade history is than the repercussions of this are all yours to deal with (and vice versa as well)
I am sure the last thing the hwbot staff wants to do is police classified transactions and I understand this, hence why I stated it should be at the buyers/sellers risk.
Also a dozen or so transactions over a course of a year is pretty good considering the numbers of transactions (100+ a day) you are dealing with in your forums.