The Blessing of Many Fractures - S1-E8
Continuity mistake: During the fight with Zhou Cheng, Cheng does a forward flip and kicks Danny, making him stumble backwards. In the shot of Cheng lying on the ground, Danny is holding his stomach. In the shot immediately afterwards, he's holding his chest.
The Blessing of Many Fractures - S1-E8
Continuity mistake: When Danny offers Zhou Cheng money, the position of the money in Danny's hand changes between shots.
The Blessing of Many Fractures - S1-E8
Continuity mistake: During Colleen's sword fight, the position of her sword's sheath and her assailant's on the ground changes between shots.
The Blessing of Many Fractures - S1-E8
Visible crew/equipment: During the fight with Zhou Cheng, Danny's face is blurred during a shot, revealing it was a stunt double. (00:45:40)
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.