Amazon has learned an important lesson about trolls and fake reviewers.

Michael Wolff’s explosive book, Fire and Fury: Inside the Trump White House, comes out today. Amazon reviews for the book at time of writing were relatively civil, which is, unfortunately, surprising. Beneath the surface, Amazon is surely working hard to keep the trolls at bay.

Last September, fake reviewers came out en masse to leave one-star reviews for Hillary Clinton’s What Happened, her book about the 2016 US presidential election. The split between five-star reviews and one-star reviews was clearly unusual, with an uncommonly high percentage of reviews left by unverified purchasers. It took the company half a day, but Amazon ended up deleting at least 900 reviews it said violated its guidelines.

Wolff’s book has been equally popular as Clinton’s. Following a cease-and-desist letter sent from Trump’s lawyers to the author, Wolff’s publisher decided to move the publication date up by four days. But for such a controversial and popular book, the Amazon review section has stayed surprisingly quiet.

This morning before the official 9am US eastern time release of the book, there were only four reviews, three of which were verified purchases. Between 8:20 and 8:40am, two reviews had disappeared from the page, both verified purchases.

A spokesperson from Amazon confirms that the site is deleting reviews that violate its guidelines “as always.” Deleting reviews retroactively, or preventing spurious reviews from appearing on the site at all, means Amazon can prevent trolls from posting reviews without paying to buy the book.

It’s clear that Amazon is watching the page carefully, though not entirely consistently. Amazon has not returned request for comment on how many reviews were deleted or why. One review was originally posted as a non-verified purchase, then later switched to verified.

It’s clear that people with strong opinions are watching the page, and this is not simply a case of unusually quiet internet. That review, the earliest that still remains on the site, has 77 replies, written with exactly the kind of respect and level of discourse one would imagine on a 2018 message board. That’s about the same number of comments the book itself has, likely because Amazon is not reviewing responses to reviews.

At time of writing, there are no reviews from unverified purchases on the page, but there are plenty that are clearly not about the contents of the book.

Deleted

A real purchase, not a real review:

Quartz/Thu-Huong Ha

A real purchase, seemingly a real review:

Quartz/Thu-Huong Ha

Not deleted

A non-real purchase, seemingly a real review, later changed to a real purchase:

Quartz/Thu-Huong Ha

A real purchase, not a real review:

Quartz/Thu-Huong Ha

A real purchase, seemingly not a real review: