pprunefan#1,
Don't blame the fin, blame the aircraft! The aircraft has to be controlled, not just part of it ("The tail rotor is big enough, but the fin robs power, don't blame the tail rotor....")
As far as how and why all this is done, I was the pilot who trimmed the fin on the S-76B and also on the A, and I know this stuff a little!
Regarding the spinning in your first case, I assumed when you said the pilot doesn't use full pedal, that you were advocating that he left some control unused. Now you are saying that there really is pedal travel but no more control. Which is it? If he leaves control unused and loses control, its his fault. If the yaw has no more power, and the aircraft spins, it is the aircraft's fault.
I think you have all kinds of interesting issues spinning in your head but one I really disagree with is simple - if your helicopter is inside its envelope and it goes out of control, do not call it pilot error, call it crappy helicopter. To make excuses for poor helicopters is foolish in any case, unless you want to lose your job and your life, or unless you think blenderpilot and I are stupid, since both of us have more time on the pedal stops that we care to admit.
As an IP on Cobras which are notorious for their LTE, and with at least 20 LTE events under my belt, I can assure you crappy helicopters will bite you, and making excuses for them is a good way to perpetuate their existance.