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.
You bring many good points for sure with rep and other things, re-peat Karens just cause they got paid to do so or other incentive, that's deceptive. We get they exist and shouldn't be enabled either to incinerate some one's personal/online/business reputation and false law suites and all. It's such a complicated topic to explore to fully go into it.
In this specific litter case or others of the likes...well clear damages/harm/loss were experienced. Like you pointed out, some companies take great intimidation tactics, often underhanded on top of illegal to suppress the critic in question making the affected reviewer more squashed and made to look un-credible when they actually are. It's a slippery slope and hardly anyone can fully grasp a 360 perspective. This gets even deeper in the case of whistleblowers as well occupy that same dualistic concept and would often be faced with backlash and campaigns to discredit of some sort. Where do they fit in in all of this? Like I said, it's not really a black and white topic...there is bends all over. You affect one thing, you throw something else unforeseen completely off balance elsewhere.