That's harder to game, because while a seller certainly could post a negative review citing some irrelevant flaw (and I have seen that), and hope that triggers buyers who don't care, they won't stop other people (like me) from posting negative reviews too, and what I'm looking for is products with a reasonable number of negative reviews where there is an absence of reviews mentioning things I care about.

I also know first hand from selling a novel on Amazon that you can perfectly well gain honest reviews in ways allowed by Amazon, and I also leave a reasonable number of reviews on Amazon myself, so I have every reason to expect at least a portion of the reviews to be honest.

Overall I've managed to avoid buying anything that appears to have been fake from Amazon, despite having bought a couple of thousand products at Amazon over the years (based on the order page stats, and taking off a few hundred as an estimate of digital only products)

It probably sucks to be an honest seller affected by it, but I've yet to find a situation where I have unable to find a product I'm happy with, so clearly they're not doing this often enough to affect me much.

Because they contain facts which anchor them to reality and act as “proof of work” in some way.

I don’t care for a review which says “this camera takes amazing pictures” that could apply to any camera and is subjective, but one which says “the cover on the sd card slot is sharp and cut my finger twice” is likely someone who has used that specific camera, and has a specific comment, and while it could be faked - why would it be? Like the difference between house adverts that say “cozy kitchen” vs “marble countertops”, didn’t Freakonomics find that specifics increase value more than generalities because people know what a marble countertop is but a cozy kitchen is filler when there’s nothing good to say.

With fake positive reviews, the seller has an incentive to leave them up, and Amazon has no particular incentive to remove them -- you, a random user, has to somehow convince Amazon to take them down.

With fake negative reviews, the seller has an incentive to get them taken down, and has the data to prove that the reviewer didn't actually buy the item. (Actually buying all your competitor's items to leave fake negative reviews about them would dramatically increase the cost of the tactic.)

End result: ignore positive reviews because they're easily faked, check negative reviews because they're probably accurate.

Especially since, you know, GTP-3 is a thing, and its effects are going to be felt pretty soon.