Insubstantial posts doesn't really rely on word count. Your could write a lot that wasn't really relevant and still insubstantial, and you can also be substantial in a handful of words. It just depends on the context, though lots of short posts with not mucn though gone in to them will probably get you into trouble.
never happend to me but there should be 1-2 warnings before you get temporary banned in my view!
Yeh the banning is essentially your first warning.