I didn't think of that. That's true, a decentralised system would make reviews immutable (negative, or positive, fake or real reviews would still persist).
Does anyone have any ideas how to solve this?
Does anyone have any ideas how to solve this?
If you are happy to pay for this, then there are a variety of options with a sliding cost/usefulness/accuracy scale.
If you are looking for reliable, accurate, balanced reviews conducted by anonymous ethical independent agents, and you don’t think consumers of that information should pay for it, then I believe the answer is there is no perfect solution that satisfies all those constraints simultaneously.