The best indicator of credibility is the quality of the review itself.
I think a reader bears the responsibility of considering and working through for him or herself the questions that you've raised. It's no different than reading someone's advice in a thread; you know how to distinguish good, thoughtful advice from the bad.
If you think that people need to be "protected" from bad reviews, then I think this is hopeless. Set up a voting system or whatever, but (1) it's no more credible than the review itself, just adds another layer of opinion on top of opinion, and (2) readers will still filter the data through rose colored glasses anyway.
I think a reader bears the responsibility of considering and working through for him or herself the questions that you've raised. It's no different than reading someone's advice in a thread; you know how to distinguish good, thoughtful advice from the bad.
If you think that people need to be "protected" from bad reviews, then I think this is hopeless. Set up a voting system or whatever, but (1) it's no more credible than the review itself, just adds another layer of opinion on top of opinion, and (2) readers will still filter the data through rose colored glasses anyway.