If someone rates any area less than 5 stars, require that they give an explanation as to why.
It doesn't have to be long. A 10 word minimum is probably good enough.
Without this, guests will and have left poor ratings with no explanation as to why it was poor. How can I improve my listing if they refuse to say why?
The overall review is not enough because often I have had guests leave 5 star overall reviews, but lower ratings in other categories and they don't mention it at all! I even attempt to ask them afterward and they almost never respond.
So how can I possibly make my listing better if I have no feedback to go on?