I think it's hard to say something to the guy you're dancing with, but I'm not sure why that should be so really.
I've had a word on a couple of occasions with guys dancing with other people near me that were likely to cause damage, and have refused my partner drops and aerials on safety grounds before, but to actually comment to my partner seems difficult for some reason. Maybe I feel some responsibility to be polite if they have asked me to dance (or some other such nonesense excuse). I don't quite know how to explain it.
It takes a lot of guts to say to someone 'I think what you're doing is wrong', and for some of us shy, sensitive little flowers
(where's Daisy Chain when you need her?) it can be quite a daunting prospect to say something to a guy, and even more so if you believe them to be a 'better' dancer than yourself...
I agree that women should be more clear about what is and isn't acceptable, but it's one of those 'easier said than done' scenarios I'm afraid.
S. x