Some people have tried to manipulate the Amazon search rankings, but it’s usually a futile effort.
One of the ways that people attempt to rank near the top is with fake reviews. They’ll contact some unscrupulous company that has people who will post 4- and 5-star reviews of products they’ve never purchased.
When Amazon catches those folks, they not only delist their products, they also sue the person who solicited the fake reviews.
In other words, it’s most certainly not a good idea to practice Amazon black hat SEO.
If you’re serious about Amazon SEO, follow the rules. Optimize your product listing for keywords and practice outstanding customer service.