There are many websites offering pre-submission review services for a fee of several hunderd dollars, e.g., editage, editeon, enago and others.
In general this seems like a useful service - instead of waiting several months to get feedback from the journal referees (and probably a rejection), the author receives feedback after a week, and can then improve the paper and submit to the journal.
However, just like there are predatory journals, it is reasonable to fear that there are "predatory review services", that take your money and produce a worthless review.
So, my question is: what is a way to detect a good pre-submission peer-review service, and distinguish it from a predatory one?