I was playing a campaign with my friend earlier and spectated one of his battles. As his Zhao Yun dueled Taishi Chi, the usual "Duel" bar popped up on the top right of the screen showing the health of both guys.
As spectator though, I for some reason had the "Run Away" option underneath their duel bar at the top right of the screen. Me, being curious if it would work since I'm only a spectator, decided to click it. Right away, my friend's Zhao Yun ran off, making him lose the fight.
I'm going to assume that it wasn't intended for spectators to have any sort of say in someone else's battle? Just wanted to point this out.