1) A reasonably intelligent person can simultaneously hold multiple, even contradictory, views of something. My point is that I don't believe you are unable to separate and extract a reasonably objective evaluation of a sexual performance of a girl.
I think people just don't bother, and justify it as being "completely subjective, and anyway, YMMV."
Do you really write reviews with only you're own experience in mind, with no consideration of a wider context?
I enjoy watching shitty movies. I make fun of them. I have a great time with my friends mocking stupid trash like Fast and the Furious or Saw. I enjoy them, because I find it amusing to watch idiots fail at making movies (yeah, I understand both are multi-million dollar franchises), but as an objective "performance", they are shit.
Yet, no matter how much fun I might have watching trashy movies, I still wound't give them a 10. I know that the average person isn't going to enjoy them as much as I happened to, and I know that the films don't deserve (in a cosmic sense) a high rating. I know that my enjoyment comes in large part from who I am, and that the average person won't be experiencing the same thing as I did.
So, no. I don't think you should give a girl a 10, just because you happen to like HJs. And I don't think you should use the "subjectivity/YMMV" excuse to do so. The reviews aren't to catalog your dates for you, they are for other people - and you know you like a very specific "kink".
2) Additionally, your ratings should be consistent. If you were just really horny that day, she doesn't deserve +2 points. You shouldn't complain about everything in the review, and still give her a positive score. You can't use the little descriptors next to the number, without using your brain.
I've forgotten it was a service a number of times. And yet, those providers didn't get 9's (forgot it was a service). They didn't deserve 9's. The session only went the way it did because of who I am and how well I clicked with her, and you or some other guy might not have that great of a session.
3) Looks should easily be divorced from performance. "She was good looking, so I enjoyed it. But, she's a terrible provider and if she wasn't so attractive, I'd feel ripped off, etc..." Or: "She was fat and ugly, but she tried everything she could think of to make things happen." See how easy it is?
4) YMMV is an important thing to remember, but it doesn't cover the vast canyon which separates your 10 from my 10. "She's a ugly, toothless tranny. But afterall, I love ugly, toothless trannys. 10/10! YMMV.