@bruno257
There is no need to post a 'secret warning'. The review process is blind, so that neither party can see the other's review until the reviews are published and it's too late.
@Megan160 's guest did not leave a bad review in retaliation for what she wrote in her review. She retaliated because she was brought up on the damage and asked to pay for it and, no doubt, the guest guessed an unfavourable review was to follow.
So, there is no point in being secretive in the review. The guest is not going to see it before they leave theirs, or until 14 days has passed since check out if they choose not to leave a review themselves. That's just how it works.
The pretty standard way for a host to let others know that the guest was not okay, without going into specific details, is to write "better suited to a hotel", but that doesn't give us much information.
Another way is to write a generic review but leave low ratings, because the guest doesn't get to see the latter even after the reviews become public, but future hosts can. However, again, this doesn't provide future hosts with much information about what actually happened.
An honest review is the better way forward.