I know 100+ author/publishers who sell on Amazon.
Sellers do not remove reviews. They do not have the control over what stays and what goes.
Your negative review(s) included references to the reviews, rather than the product. Someone, no doubt the seller, flagged it using the “Report abuse” button. An Amazon gnome likely looked, thought your reviews were not on-topic, and nuked 'em.
Are there fake reviews on Amazon? ABSOLUTELY. There are folks on Fiverr and other similar sites who offer such services that “guarantee your product 100+ reviews,” which won’t mention that they’re all fake, but they very obviously are.
The solution to getting such reviews bounced is to report them, as mentioned above. Click the Report Abuse button and point out the specific user accounts. Do not write a review and refer to other reviewers, especially those with whom you disagree. Amazon hates that.
I know several cases in which Amazon deleted phony reviews, sometimes one at a time, others in mass deletions, when they were found to be fakes.
Another thing that will get a review deleted: if you’re one of the seller’s competitors. And yes, they are more quick to respond to such things if you’re a MEGA seller; not some tiny Chinese corporation, but, like, Penguin or HarperCollins. (E.g., just the other day, a well-known controversial author’s most recent release received a 5,000-word, vitriolic screed that was more of a New Yorker article than review. The author himself responded to it. (Which is usually a very bad idea, but I digress…)
I think this discussion ended up getting flagged–the publisher (Penguin) probably got involved–and Amazon temporarily deleted the review, and the hubbub/speculation is that they contacted the reviewer and asked him to submit something less personal, if he wanted. The guy did so and the newer, toned-down but still negative review is up.
(I think part of the reason this was a successful take-down was because it seems pretty clear the reviewer is himself an author in the same general field. As mentioned, that’s a no-no.)
Anyway. Point is, there are all kinds of ways to game the system. This includes purchasing fake reviews, offering compensation to people to download your book (to boost rank) or speed-read through KU books (which are paid per page-view), massive 3000-page books stuffed with crappy fake extra content (again, to add page-views for books in KU), and other such ploys. From time to time, Amazon swoops in and nabs the perps, stripping their products’ ranks or even taking the product down altogether.
But with so many sellers and products on Amazon, they can’t catch everyone. It is definitely wise to be aware of possible fakery and keep your eyes open for suspicious patterns in reviews (such as the OP mentioned–text that sounds all alike, and reviewers who all seem to be reviewing the same group of books). When you spot potential phonies, use the “Report abuse” or, even better, simply click “No” beside the “Was this review helpful?” text–or even more important, click “yes” beside the reviews that did seem legit. Reviews with the most “helpful” votes are usually bumped to the top, while those that are least helpful will fall lower.
And yep, it’s often a good idea to pay the most attention to the reviews in the middle of the pack: 2-stars to 4-stars. (In my experience, it’s the 3-star reviews that tend to be most helpful; they often give the good and the bad.)