Unfortunately, the laws in each country are very different. I will therefore describe some aspects of my understanding of the law. Of course, this may be different in the countries and legal systems of the other participants.
In my view, the RFAA idea presented by Amir could at least achieve the following:
1. reviewing the legal status for possible lawsuits: where are they possible, what precautions can be taken to tie them to a specific jurisdiction, how can lawsuits from other places be averted due to lack of jurisdiction, etc.
2. ensuring that manufacturers can object to measurements that have been taken: Assuming that manufacturers are not just suing for the sake of a dispute but have existential concerns, for example, you would need to be offered an acceptable form of clearly positioning a counterstatement. This could, for example, be a separate part of the forum with a link directly after the test result. This feedback could then be directly visible to everyone without a response from a third party and thus offer every manufacturer the opportunity to openly position their response to the test results without surrounding third-party opinions. This could be seen as a protected space that reflects the interests of the manufacturers.
3. review system: By this I mean the comprehensible and comprehensive presentation of the principles of the reviews carried out. Their subjective parts, essential measurement methods or possible fundamental weaknesses of the work. This would certainly be a lot of work that would also generate a considerable amount of costs. But in my understanding of the law, it would be necessary to explain transparently what the site and its reviews do and do not do.
4. dealing with legal disputes: This means a transparent but also author-protecting procedure which, in the event of legal action or, if necessary, successful legal action by the other side, shows this on the homepage in a legally secure manner.
This could be an area in which, for example, information on withdrawn reviews or reviews pending litigation is stored. For example, if I search for reviews of the manufacturer XXYYZZ in the forum, I find the note that the review of product 112233 has been removed from the site due to a legal dispute or the note that the review of product 112233 is being legally contested by the manufacturer.
This would satisfy the (legitimate?) interest of the manufacturer not to conceal the criticism and the visitor to the site is informed of the position / behavior of the manufacturer.
This would also be developed as legally secure as possible thanks to the idea presented by RFAA.
I could imagine that with such an approach, on the one hand (also as an example for other sites on the Internet with reviews), a somewhat more legally secure basis would be created in order to be able to continue the work with composure and, on the other hand, the transparency that we all value so much would be maintained can.