From personal experience Yelp is a company I do not respect or trust in anything. Yelp absolutely don't care about small business and how their filtering system works. My wife is running a small business and she has been facing exactly the problems described in the article. Real customers posting real reviews but quickly disappearing in the filtered reviews for unknown reasons, some of her customers have been on Yelp…
Yelp are in a hard place, they show negative reviews about peoples businesses. People who work there, or own the business absolutely hate this, because it could cost them there business. Nobody likes having their work threatened. And most people who own businesses think they are doing a good job, and don't like criticism. They take it very personally, and blame Yelp rather than the reviewer.
Since my wife started her business, she has met various other business owners with similar experience...
Hard to believe that their filtering system is not directed toward the good of Yelp business plan for selling ads.