[tryitnow]

"but internally at Amazon the Seller Performance team is separate from their Community (user review)"

Indeed, my suspicion is that organizational politics have more to do with the lack of a better rating system than any technical limitation.

The approach I use is to read 3 star ratings first before biasing myself with the more extreme ratings. I also check to see what else the reviewer has rated and if there's nothing there then I immediately dismiss the review.