In perfume trading groups I have participated in each person who sells or trades has their own thread in a reviews section of the website or in a feedback thread in their own journal. Buyers/ traders are encouraged to leave comments regarding trades once they arecomplete, and trustworthy traders soon accumulate añd give many glowing comments.
Less than stellar comments may be replied directly to by the reviewed with their side of the transaction, but negative comments are uncommon - its a positive reinforcement. System that encourages everyone forrest each other well and saygood things when there is good to be said.
Here is a link to my perfume trade journal with links to my feedback 0ages
EJ's Journal