One thing I've found - and I'm probably not alone in this - is that in general once mechanics get involved, most of the roleplay goes out the window.
Sure, there's been some glorious exceptions - I fondly recall one combat I ran where the characters kept their pre-existing and rather humourous in-character discussion/argument* going right through the battle, yelling their points and counterpoints across the line to each other while they beat up their foes - but those are very much the exception. Usually, once initiative gets called there's little if any in-character speech until the combat is done.