OK as it turns out I need those microbrushes to get the effect I want for one of my features. So...
-What makes a brush a "microbrush"?
-What problems can a microbrush cause?
-If I leave my microbrushes in, does it affect compiling or gameplay? I haven't noticed any difference.
-Edit: As it turns out I didn't need those microbrushes after all. Sorry for wasting your time.