What is itrader? I'd post this in the buy/sell/trade section, but I don't have enough posts to do that yet.
You could read the forum faq's to find out. But in essence, in the bst forums, if you are a seller or a buyer, you can then use itrader to give a score to the seller/buyer. They would also do the same to you. It shows other sellers/buyers that someone with itrader has done business before and might be better trusted to do business with. Looking at itrader before buying/selling to someone, you can see if they have been given good rep or bad rep.