Some even use little emojos on their phone, I know this to be the case with a few ladies I've seen.  I won't even mention some of the messages I've received, but when I read them I know they had just as much as good time as I did.  

... is similar to the Intel that is shared by strippers in the dressing rooms. Ooh to be a fly on the wall

so much of a "rating" as it is an evaluation of financial depth and potential to repeat often.  Providers will decide early on what your hobby level is like and how much time and effort, if any, they want to put in to try to recruit you as a "regular."   Once you achieve "regular" status, I don't think there is too much locker room talk between providers about their clients other than what is necessary to provide a reference.  You're not going to hand over your "secret sauce" formula to a competitor.  

In the name of discretion all I share is if the client was safe and respectful, and if I'd see him again.
If it is more detailed than that is it likely because the client was unpleasant in some way.. so from the ladies side the less that it said about you the better in most cases.

Oh I could see the hurt egos now. Also we really don't look at our clients as numbers, we know you have names and feelings and are human and not perfect every day.

Spoilers~

1) Didn't like him- wouldn't see him because something about him irked me in a way that didn't feel worth the money he paid
2) Had a decent time- no major complaints- all went well- would repeat
3) Had an amazing time- great chemistry and/or ultra-cool vibe about the client- will be excited the next time he contacts me

I'm lucky that the vast majority of my clients fall into Categories 2 & 3.

I don't notate these ratings anywhere, but I remember them.  I'm sure that when I give a reference, even if I provide very little detail beyond the fact that the guy is safe to meet, a smart lady might be able to discern which category a guy belongs to based on the tone of how I answer the referral.  IE., there's a difference between writing "yup, I've met him and he's safe to see!" And writing "omg girl I've met him and he's great.  Have fun!"

I don't formally keep reviews/ratings on clients but I know who I will definitely see/not see again. 'Definitely see' would be anything from a decent time to mind-blowing for me. 'Definitely not see' would be giving my weird vibes, crossing boundaries, poor hygiene, rude, etc.

Handsome edgy brooding artistic Montgomery Clift type that's a sexual dynamo.  Instead the most I get is "safe, calm and easy".  Sigh.