Require strict KYC of all reviewers. This should be no privacy concern since it's about B2B contracts that operate in public between two registered businesses.

Require strict KYC of all reviewers. This should be no privacy concern since it's about B2B contracts that operate in public between two registered businesses. Don't publicize who wrote a review, but keep it on hand for subpoenas. You are probably not liable for defamation if you can identify who wrote the review - and they should be able to prove it's true. Ask a lawyer first of course.