If and when I have/had a problem with a Parts Supplier , I would try to work it out with emails, PM's and by phone first before airing it out on the forum. as I would hope every one else would to.
this is for the parts for sale/wanted section.
but like above , I would try the PM's, emails first. but if all else fails. all I can do is post in there thread my problem with them. then it just go's away into the pages to be forgotten.
if there was a feedback section a buyer could go there and see there track record. and make the decision to buy from them or not.
in the section , once a buyer posts feedback, the next buyer just needs to add there feedback to the same thread. there is no need to have 2 - 10 treads for the same seller.