Great thread. With that said…
ROTS
Grievous’s cough. I think it’s actually a pretty good way to immediately establish that he’s not just a droid, and to sort of anticipate Vader’s breathing. Not sure what about it people hate.It’s partly that he’s just constantly doing it, and it’s more distracting than Vader’s breathing. It’s partly that they explained it in an EU source, which is annoying (Vader’s breathing aside, again). But it’s probably mostly because the character is annoying to begin with so the cough just makes it worse. I think it would bother me less if Vader was doing it.
I don’t think he does it that much as you say. And any explanation is unnecessary. It’s easy to assume that the technology just isn’t perfect or whatever. As for the character being annoying, I won’t argue about that.