Valve: Positive “Review Bombs”

Valve writes: "In our recent post on User Reviews Revisited we covered our process for identifying off-topic review bombs on games, and how you can decide for yourself whether or not you'd like to see them included in Review Scores throughout the store. Back in 2017, we defined a review bomb as an event where players post a large number of reviews in a very compressed time frame, aimed at lowering the Review Score of a game. At the time, we wondered if there'd be "positive review bombs", but there were no examples of one. We decided to wait and see."