Quote Originally Posted by bitpicker View Post
Would there actually be an audible difference between слушаю-с and слушаюсь?
In modern language, yes! Слушаю-с - the final consonant is hard (unpalatalized), слушаюсь - the final consonant is soft (palatalized). It is very audible for Russian ear.
In older language, there was a tendency to pronounce final -сь in reflexive verbs without palatalization. But this pronunciation is outdated.