On the subject of commanders behaving badly, this is the funniest result I've seen:
Playing Arcosephale, I set my commander to "stay behind troops". My elephants attack, get chomped, rout. They crash through my lines, but I've intelligently placed my commander off to the side so he doesn't get trampled.
Next turn my commander decides to move "behind" my elephants.
*trample* dead commander my entire army routs
I've found that setting commanders to "holdholdholdholdholdstaybehindtroops" keeps the commander in the back where you want him rather than charging with the front line.