one of the most powerful things a strong writer does is ADAPT to his or her "communicative situation." (perhaps this is some version of "proper words in proper places.") all i know is that any discussion about what makes a certain writer effective must include the ability to adapt to the situation at hand. yes, i mean audience, but i also mean so much more than audience.
simply put, the key to effective writing is an ability to adapt to context, to the forces motivating the writer to speak.