It exist in the iTrader feature.
When you click on a username you can see the feedback they received. In Your case, you haven't gotten any feedback so you see 0% (when you deal with sellers, make sure that 0% represents no feedback rather than just negative feedback because it can say both), but for those who sell here regularly you will see some sort of percentage. It is also clickable so you can see the context in which each feedback was left.
Every good feedback adds a 100% to the average, every negative adds a 0, and neutral keeps the rating as it is (excluded from the calculation). For example: someone with three feedbacks: good, bad, and neutral would have a 50% score.
If someone only received only one feedback and it was neutral, I think it shows 100%, but I'm not sure.
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