I think that eBay views seller feedback as a marketing tool. The purpose of seller feedback is not to allow a buyer to objectively compare two sellers. It is to make buyers feel comfortable buying from most sellers.
Look at the star system. If you were to see something rated as 4.5 stars, you might think wow that's 90 percent out of 100, this guy must be on the ball. In reality, you have to be completely incompetent and careless to drop to that rating. The exception being someone with a very small sample size of sales, like 1-5 where they just get unlucky.
Additionally, the way feedback is displayed now usually highlights the most rave reviews. I assume they have an algorithm that picks up on certain words and also might highlight longer feedback messages.
If the point of feedback was to allow buyers and sellers to make an informed interaction, they would have a completely objective metric. A seller would be able to see how many returns a buyer makes, INRs, etc. A buyer would be able to see the same thing for a seller, essentially how many successful transactions. They also might be able to see things like how quickly are items shipped on average.
Feedback has never been that big of a deal on eBay outside of extremes. For 99/100 buyers or sellers, what their feedback profile says doesn't matter. I think most of eBay's marketing efforts with feedback and the Buyer Protection Program are based on countering the flea market image eBay at one point had. They want buyers to feel like they are buying from reasonable sellers because back in the day they had an uphill battle to fight against the marketing perception that eBay sellers were random people and you had no idea about the quality of the item or service you would receive. While that is still true, I think they want buyers to feel like they are guaranteed some sense of quality. The Buyer Protection Program and displaying only the best possible feedback creates that image.
