Over 2,400 Steam users had their accounts restricted for marking a negative review as helpful

pcgamer.com:

Beneath every user review on Steam is a prompt that asks «Was this review helpful?» and lets you respond with a Yes, No, Funny, or Award option. While it makes sense that user reviews can be flagged as inappropriate and those who write them have their ability to post more restricted, it turns out that even clicking on that thumbs-up «Yes» can get you in trouble, as 2,439 people who labeled a negative review of Warlander(opens in new tab) helpful found out.

Warlander is a free-to-play game of multiplayer hacking, slashing, and magicking. Like a lot of competitive online games it uses anti-cheat software, in this case Sentry Anti-Cheat, and there are players who hate it. One, who goes by FREEDOMS117, posted a negative review earlier this year calling the anti-cheat system «suspicious», claiming that «it maintains running even when the game is closed, including tray icons» and «seems to be sending some packets of data to japan IPs while the game has already been closed.»

FREEDOMS117 went on to explain how to uninstall Sentry Anti-Cheat completely, including instructions on how to remove anything it left in your registry. If you sorted Warlander's user reviews by «Most Helpful» that review was at the top, receiving not only 2,439 upvotes but also several hundred awards. 

Until mid-April, that is, when it was banned by a Steam moderator «for violating the Steam Terms of Service». You can still see the review with a direct link, but its text is now hidden(opens in new tab).

FREEDOMS117's Steam account was then restricted for 30 days, locking all Steam community features. That made it impossible for them to post further reviews, post messages in the forums, or vote on other reviews, though their ability to play games was not