I am looking at it in a trading sense because an auction system is an entirely another project (that I would LOVE to have!). As in the trading sense, I believe what you said is correct. All it has to do is let 2 users rate each other and link to the thread that was initially started.
ie.
me) I have a Star Wars Darth Vader figure for trade.
Bob) I will trade my Luke figure for it!
me) Deal!
Bob) sounds good! I'll e-mail you to finalize the deal!
me) I just got my Luke I traded with Bob and it is great!
I then could trade rating feedback with Bob. Now, it could be like ebay: SirSteve (124)
the 124 would be the feedback count that links to all the feedback you have recieved.
I dunno... just thoughts...