The best thing about speechless main characters(IMO) is that you can make up their own personality! You can imagine what they say- what the verbal equivalent to Mario' s " Uuuh huh!" in Paper Mario is! You KNOW how pissed off Link is when he makes those screams, because YOU' RE him! Can you imagine a life where Link could talk? Outrageous!
Hate it. Hate it, hate it, hate it. We' ve had a hundred years of cinema and TV in which nobody has had the remotest difficulty empathising with the hero or heroine, even if they had a personality diametrically opposed to ones own.
Singling out the actual protagonist to be a silent character does more to jerk me out of the " reality" of the game than any other factor. Create the characteristics and skills all you want, but if there are only a few basic character models to begin with, where' s the problem in having them each have a distinctive voice?