Re: STAR TREK INTO DARKNESS - Grading & Discussion [SPOILERS]
I would point to TMP as evidence that rank doesn't matter when captaining a starship. Admiral Kirk wore captain's stripes when he took over command of the Enterprise.
IIRC, if an Admiral has command of a ship, they are still referred to as Admiral. Kirk actually demoted himself in rank. That's the difference. He expected to KEEP command of the Enterprise
"If the world was perfect, it wouldn't be." - Yogi Berra