I always took that as the writers winking at the viewers; it was impossible to read anything online about Iron Fist without someone mentioning that he always said that. So Luke cut him off. There was also a pretty fun scene right after Luke escaped from that guy's makeshift lab with the metal headband still on and the clothes he'd stolen from someone's backyard clothesline. He looked basically like his comic book incarnation, but he caught a glimpse of his reflection and said "I look like a damned fool!" Nice commentary on how flashy comic book colors usually don't translate well to live action.
Speaking of Luke and Danny, though, I did like it when they teamed up; Danny would smash his Iron Fist into Luke, and the resulting shockwave would cause ridiculous devastation. I think that might've been in The Defenders after they were all together.