Yeah I guess that's why reputation is also important on the reviews, hive does save you with the immutability but if you're someone who just goes around and leaves bad reviews cause you're in a bad mood or have a vendetta against the brand/product/ or are being paid to do so by competitors/etc, then there should be a reputation factor in play as well that let's readers know this particular reviewer has had a history of false/fake reviews so their review shouldn't be trusted.

It wouldn't even necessary have to be tied to hive itself, the reputation here is very bad and most of the time doesn't mean much. If there's wars spawning due to these reviews with downvotes, etc, the community should then step in to counter the "bad" downvotes if the reviews are legit and the user has a good reputation history for reviews.