@Ivan451
Yes, this is the problem. A few months ago, a guest left me a nice review, nice private feedback and low scores. I had a feeling that she didn't understand that a 3* was bad (turns out I was right) so I messaged her but she never responded. She did get back to me in the end, but only because I then messaged her aunt, who is a Superhost and who understood why I was upset about the rating. Obviously, this is a really random thing (the aunt had contacted me about the listing before her niece had booked) and one wouldn't normally have had this recourse. Without the aunt, I'm pretty sure the guest probably would not have checked her messages.
In addition, when she contacted CS to ask for the review to be removed, she was told it wasn't possible as more than two weeks had passed. Meanwhile, I was speaking to a rep who told me it was possible to remove the review. The rep she was talking about was clearly confused. The two week deadline is for writing the review, not removing it. We eventually got it sorted, but it wasn't easy. The guest could easily have given up in frustration, saying she tried, but was told by Airbnb it was impossible.
PS I read ages ago on the CC that Airbnb were introducing a system to tackle 'outlier reviews'. This basically said that when a guest left high scores in the individual categories but a low score overall, e.g. 1 or 2*, a message would pop up asking them if they were sure and reminding them that they'd just scored highly in the categories.
I have no idea if this was ever implemented or, if it was, if it works. I asked CS reps about it a few times but they had no idea what I was talking about.