I agree, if a seller deals with a return or refund professionally, then they deserve a positive rating. I've not had a lot of experience with it, just once when I had a fairly cheap item replaced because the original was faulty.
It's normal for a seller to ask for photos or some sort of proof, that's just good business practice, but after that, a timely response deserves a positive rating.
Sometimes when I read feedback where something has gone wrong and a seller has responded well, that is more relevant than just the good experiences as it shows that if there is a problem, you can rely on the seller to deal with it.
I think, as you said, there is a difference between the seller and the transaction as such, and the quality or otherwise of the product.
I have noticed that with feedback, people can now give much longer responses so i think buyers can now cover both bases if they need to.
