Can't seem to find a direct way to do this.
I was leaving feedback for a seller. (We cancelled the transaction and I'm ok with that because there were some issues but the seller was really good about keeping in touch with me.)
The feedback score for shipping charges was blocked out for me because it said that free shipping is automatically 5 stars. Shipping was not free when I originally paid for it (and was refunded, and shows on my original order details) but as I was leaving feedback, it did say "Free Shipping" and now this seller automatically gets a high score.
Hmmm...!