Lead Horse Back to Stable - S1-E11
Revealing mistake: When Danny and Colleen are fighting in the rain at the end of the episode and Danny starts explaining how they should stop fighting, raindrops from the camera can be seen dripping from the top left of the screen.
Lead Horse Back to Stable - S1-E11
Continuity mistake: When Davos is talking to Claire in the kitchen, his hands are behind his back. But in the shot before they go sit down, his hands are to his side.
Lead Horse Back to Stable - S1-E11
Continuity mistake: When Davos rolls Danny over, Danny's right hand is on the ground. In the next shot, it's resting on his stomach, but is then back on the ground before he summons the iron fist.
Answer: In the comics Iron Fist is able to use the power on both hands. There is no reason why Danny shouldn't be able to. Presumably he chooses to only use the one fist at a time, focusing all his power into one hand rather than distributing it between 2.