Maybe something similar to the Buying/Selling thread, but where every user gives out how own badges:
A Trading Experience Thread
One post per user.
In this post one writes down all the other forum users with whom one has traded or had experiences and one’s rating of them.
If you are a trusted forum members then others can make up their own mind what to think of your judgement and given out badges.
This way badges given out by trusted forum members will automatically have more weight than if someone unknown or new would post their ratings.
A post in the thread could look like this:
< Post by JAAJ >
User A: Trusted Trader
User B: Trusted Trader
User C: Suspicious Behavior
User D: Trusted Trader
User E: Confirmed Scammer/Thief
And then people who want to check about whether someone is trustworthy partner for a trade, can go to this thread and use the search function to search through for “User X” and check everyone’s rating on him.
If then they see that “User X” has been given a positive rating by other trusted forum members, then most likely User X is a safe trade partner.
Which also means that new forum members will not have any psotive badges and might just be listed as “Unknown Trader”, making sure that they always have “to send first” in order to earn a positive rating from someone.