Of course it returns negative results. The key is not to take them blindly.

If they mention specific facts (extra bonus for verifiable ones), do not sound like ones written by poopheads or mass produced by competition, then it's a very strong red flag.

Things like unfavorable terms of service or checked-by-default, hard-to-notice checkboxes subscribing you to worthless additional services are easy to verify, even if you give zero trust to anonymous reviews.