I know nothing about iTrader. From what I see though its a feedback system. If iTrader works by throwing a user into a special page to give feedback you could modify things yourself.
Simply edit the language string that sends the auction or ad closing email which has our system feedback page link and replace with the appropriate url to your iTrader install to add a feedback. I am assuming this is how it works.
You could even if adventurous edit your profile template to link to feedback for specific users in vb
not our page.
Those would be simply two very simple link changes.