(Mostly answering to the deleted grandparent here.) "In the meantime, they benefit from charging businesses to allow positive reviews to appear and to suppress

(Mostly answering to the deleted grandparent here.) "In the meantime, they benefit from charging businesses to allow positive reviews to appear and to suppress negative reviews (if they're doing that, it would explain why they don't focus on credibility)." We try to address this issue in our paper. Take a look at Section 3.4. Short summary: we do not find any noticeable differences in filtering between advertisers and non-advertisers, but there are limitations to our analysis.