I like information. When looking for a petsitter I read all of their reviews both for obvious remarks and possible coded language.
Same with looking for a housesit. If previous sitters don’t comment, then I assume that either the owners, the house or the pet were an issue. I would be unlikely to apply for the sit.
I welcome a private way to help a homeowner or a petsitter know how they could enhance the TH experience. Most often that’s about cleanliness or needed repairs (I petsat one place where both the toilet and the kitchen faucet were not functioning correctly). I have been guilty of leaving a 5 star review because I liked the location, pet or people, even though there were aspects that could have been approved upon. I’d rather let them know, privately.