@Huw42
I don't know your legal requirements buy I would think as long as your negative review is written with your business head not your personal head.
Business head understands even though something is obviously true. There is a big gap between obviously and provable.
Also a business head is aware a review is not only seen by Hosts. It is on the internet available to guests, competition or anyone.
I will post a negative business review. My last one said communication was lacking causing minor inconvenience. All true. All provable. She did something I felt rude and didn't apologize. She is obviously inconsiderate but if I look at that with my business head, making an assumption no matter how obvious is an assumption. Not a good business comment on a public forum