They hide reviews of newly active users without histories. The idea (at least) is to prevent fraud of owners asking their friends to make yelp accounts.
Was that always true? I had a call from Yelp at work where one of the selling points was controlling your profile, in which they mentioned "removing spam" and "offensive reviews" (they might have said "fake"). I took that euphemistically when combined with rumours I'd heard. But that was some years ago (maybe 5+, in UK); and could have been overselling or phishing by a third party I suppose.
How do you handle offensive reviews (like swearing, libel, personal details), do Yelp really manually intervene?
Don't they remove fake reviews, in which case a business can say the review is fake.
The same way HN uses green usernames.