I think this show needs some sort of Story Line Ombudsman to remind the writers of those loose threads periodically.

Mako is shown shaking his hand to cool it off when he was slowly burning through the bars on their cell. I don't know if that was due to using his fire for an extended time, or if it was the heat from the melted bar. If it was the heat from the bar, then Korra probably would have been burned by her mask catching fire.…