In this case, the filtering happened by TripAdvisor staff and "trusted community members" with mod power. But the article also mentions "hundred of filters". I

In this case, the filtering happened by TripAdvisor staff and "trusted community members" with mod power. But the article also mentions "hundred of filters". I imagine that the filters flag comments and then the 300 staff TripAdvisor has to ensure the reviews are legit manually review them. It's possible some sort of automatic filtering glitch has occurred, but this has been an issue since at least 2010. The company is very much still responsible.