I can think of several, but here's one to be getting on with.
In the vast majority of cases where an escort hides her feedback, it's because she's dodgy. After all, bona fide escorts can dispute negative feedback if they wish, and Adult Work will remove feedback that gives personal information (such as an escort's real name, or her address).
When a girl is dodgy – or her profile is a Private Gallery scam – the feedback saying as much is likely to be "non-scoring" feedback. That is, where an official booking has been made, but the escort hasn't "confirmed" it. The feedback will then show as "Feedback Only", there having been no option to register Positive, Neutral or Negative.
If you put your cursor over a profile with hidden feedback, however, only the totals for "scoring" feedback are shown. There's no indication of whether or not there's "non-scoring" feedback, or of how many such feedbacks there may be.
The existence of "non-scoring" feedbacks on hidden feedback would be useful to know, and I'm surprised that the Adult Work "counter" doesn't include a category for number of non-scoring feedbacks – for both hidden and non-hidden feedbacks, of course.
(Others may say that they would never consider seeing a girl with hidden feedback, and in 95% of cases that is an unarguable position. Nonetheless – the more information the better!)