Someone linked to my product and wrote a one-star negative review. He did not buy my product, and the other links he gave were negative one-star reviews. How to deal with this?

It's Amazon and they don't have to buy it to leave a REVIEW.

Feedback would require a purchase (or at least an order having been placed).

Here there is nothing you can do.

Take a deep breath and suck it up. Wear protective gear and a thick skin. Amazon will kill you with paper cuts to your soul.