Since any rating lower than a 5 Star reflects the Host did something wrong, and drops their status, there should be a legend explaining this to a Guest.
As a Guest, I thought 4 out of 5 was really good.
(I reserved 5 Stars for only something above and beyond-amazing.)
Little did I know my 4 Stars hurt an excellent Host. Or when my overall rating was a 3 because a neighbor came home late with radio blaring and woke me up. This wasn't even something the Host could control, the place was very nice and comfortable, but it made my stay less than "Amazing".
Every time I Host I have to send a note prior to checkout explaining anything less than 5 is bad, and I can't control the neighbor's dog barking at a squirrel or the trash truck coming by at 7 on Tuesday...