For example, I bought a little portable projector last Christmas. In the box was a big bar of Swiss chocolate and leaflet offering me a tripod in return for a five star review. The projector wasn't as good as the description made out. It wasn't terrible, just not as good as they claimed. So I left a three star review. I started getting texts from the seller asking, and then demanding I remove the review - they weren't offering me anything in return. And the texts came from the sellers name which changed slightly every time, so I couldn't easily block them or reply to them. It took two months for them to give up and leave me alone. I've had similar less extreme experiences with other sellers.
I did complain to amazon, who said they would take action. A few weeks later the seller disappeared from amazon, so I assume they received enough complaints to take action.
But..... the seller reappearance with a different name. They had the same product range and descriptions.
Amazon doesn't care and is totally complicit in all this.
The problem as I see it is that so much commerce is concentrated on to a small number of platforms (amazon, ebay, wish etc), which leads to sellers getting desperate to get to the top in searches. I mean, I can understand sellers doing this when their livelihoods depend on it. It's still not right though and amazon should fix it.