I've never faked an orgasm either, for exactly the reason you mentioned. Plus, if I fake it, how am I going to teach him how to actually
get me off? Or anyone for that matter. It's not doing the female population any good to teach a whole bunch of guys to think they're king shit in bed when really they're about as much fun as sticking a fork in a receptacle. If I've ever been with someone and he just wasn't any good and I was bored, I usually pretty much pushed him off and said "I think I'm done now" and if they asked whether I came, I just said "no."
The people who really take time to learn a woman's body can tell if she has an orgasm. We may not squirt out sticky white goo (although sometimes we can) but there are a lot of physical signs, muscle contractions and the like. It's really not that hard to feel a woman's orgasm, if you're paying attention.
And if you are in touch with energy, like tantric practices, there's a whole other level on which you can feel an orgasm, and then take that orgasmic energy and feed it back into them to make the sky open up and see stars