I was hearing that theory a lot. He "gave his face, in trade for energy bending". Incoming possible spoilers:
EagleMan wrote: Probably connected to Koh the Face Stealer, who has a hatred of the Avatar, and is a spirit himself
Energybending - A Comparison
While the Lionturtle and Aang use the same technique, Amon seems to be using another method.
When Aang takes away Ozai’s bending, and when the Lionturtle teaches Aang energybending, they both thouch TWO points on the body, the yin tang and the ru zhong point aka the Ajna chakra and the Anahata chakra.
When Amon ‘takes away’ LBZ’s bending, he only touches ONE point, the yin tang.
Now what could that mean?
I think Amon is faking it. That he is making people believe that he is taking away their bending, when what he is actually doing is blocking a chakra.
Here is why:
Amon touches the yin tang point aka the Ajna chakra:
Yintang Acupuncture Point
Location: Midway between the medial ends of the eyebrows Actions& Effects:
•Calms the spirit - insomnia, anxiety, stress.
•Sinus issues - congestion, sinusitis.
When Uncle is teaching Zuko about lightning, he talks about bending needing a certain amount of inner calm. So, if you were to close that chakra and lock all the anxiety inside someone, making them incapable of being calm, that would effectively take someone’s bending away.
Quite clever actually, since the more terrified they are/become the more permanent this block will be. And Amon is sure laying it on thick.
Ru zhong, Ajna chakra, Anahata chakra.
Image source: One
I’d also like to note that he touches the back of his neck too. It’s really split second but he does.