I've seen some coaches treat their students really bad. They shout at them, make faces showing their disgust over the students' mistakes, etc. I've seen at least one kid look obviously disappointed, dissatisfied, name it, and I felt so sorry for her.
One of dd's coaches is passionate about skating. When something goes right he looks elated, when they have been working on the same thing for 6 months and it still is not right....he does look disappointed and so does dd. I don't think that is wrong or abusive. Wrong or abusive would be to tell her she is stupid, to belittle her, or give her a punishment or make her try it until she cries. Instead he shows video, has more off ice, and they keep working at it.
As for exaggerated facial expressions - I think it's only natural if your coach isn't a yeller. The ice is loud - sound bounces everywhere, so an exaggerated expression sometimes works.
As for a gym comparison - yes, the coach fills the parents head with dreams of grandeur. You are told (dd was 4-5) that no one gets it more quickly, that if you push them, they will be great. That scholarships roll in for elite gymnasts, banners showing the colleges are up. So if they cry, tell them you'll take them out for pizza after or you'll buy a present if they don't complain. There is a weird mind thing that happens....all the parents fine with it so you think it's YOU that is the strange one.
For us skate was totally different. Coaches were more laid back, they seemed more interested in the child at that moment in time than focusing on creating a national champion from a 4 year old in the future. I get the feeling too that they know we struggle to afford skate so we are out of the running from the get - go. It doesn't matter if dd has the talent to be great if she doesn't have the resources for time with coaches and ice. A little different from gym where we paid a monthly fee and the occasional private lesson. Gym was half the price of ice and twice the time!