I personally don't like being corrected on my technique unless someone can demonstrate to me why it's wrong - i.e. it compromises my fighting capacity. For example, my current instructor often tells me that my bow stance (Kibadachi) is too narrow and that I need to stand with my legs further apart, but I keep telling her that it opens my groin making it more of an open target. Her counter argument was that my narrower bow stance is less stable if someone were to push me from the side... but WHY would I stand at bow stance side on to an opponent in the first place?? Even if my opponent managed to hop to my side and push me, I could still drop into something like a Sitting Twisted Stance to catch myself and compensate. In the end, she couldn't supply me with a good reason as to why my bow stance is incorrect other than because it's different from hers. But she still considers my version to be "wrong" and keeps trying to correct me when I do it...
IMO if what you're doing in martial arts works, then how can it be wrong? Even if it doesn't work for you, if it works for someone else, then how can it be wrong (at least for them)?
I use vertical fist for straight punches. I don't think it's necessarily better or worse than using a horizontal fist -- the only marginal advantage of a horizontal fist is the additional 90 degree rotation which would help generate more torsion, but really you can generate a lot more torque from your legs, hips and waist (re: from your stance) anyway.
And I think punitive measures might work for people who are just plain disobedient or recalcitrant -- and if someone's gonna have that kind of attitude, they probably shouldn't be taught martial arts. But for most people who are earnestly trying to learn the technique, I think simply correcting them by explaining to them why they're wrong works better.
One thing I find with some martial artists - and my current instructor is one of these - is that they become more concerned with form over function. Everything has to look exactly right and done by the book; as if it's more important than... ya know, being able to fight. I used to work with a Japanese guy who's a black belt in 3 different martial arts who was exactly like that too -- a complete perfectionist in form, but when we trained together... could he actually use his flawless form in a fight scenario? Nope. And I'm not even an advanced fighter or anything. I've often told people that if I can beat you, then you really aren't that good, because I'm not! :eek:
So I don't like to get too obsessed about form... to me, function matters more. And this is one criticism that some people have about grading and testing -- being able to perform brilliantly in a test doesn't mean you can apply it well IRL. Just look at drivers... we all know that there are plenty of people who pass driving tests and get their drivers licences, but are absolutely terrible drivers on the road.