It's all about balancing that great term of metadiscourse. This balance covers every bit of writing out there, but from my experience, it can be difficult for student writers to figure out where to use metadiscourse and where they're using too much. After all, writing research papers and essays requires the use of some metadoscourse, but word processors don't have Metadiscourse Meters that tell you how much of it you're using.
What more is there to be written? Except for the continued advice of every teacher out there: Revise! Williams actually addresses how to revise to be concise, all by cutting down on metadiscourse. It almost seems like metadiscourse is an evil force in everyone's writing that continually attempts to remove clear information. Maybe that caters to a paranoid mind set, but it rings pretty true for student writing sometimes. When you need to make that paper's minimum word deadline of 1400 words, that's when you call up metadiscourse and invite it over for a pizza party.
Well alright, if you don't like pizza we can always order chinese.