It could be explained that Yakone somehow 'absorbed' the ability to remove bending when Aang took away his bending and that due to his original bloodbending skills he is able to resist it almost completely. However that in itself is contradictory. On top of that for a person that's over 80 years old he's quite nimble, his voice changed and then he just took the bending away of his own son.
I just had some really whack, completely based on nothing, excreted straight from my imagination theory =DD A few minutes ago I realized that there's actually a bit of a flaw in the whole Avatar - balance - spirit world - real world thingy. The Avatar is supposed to keep balance to the world, but who keeps the Avatar in balance? As the Avatar is only one person, that's actually a complete 'unbalance' in that entire system. So what if when the Avatar spirit came to the real world, another spirit came alongside with him to balance him out. After all if someone suddenly gets the power to bend all 4 elements, it's not too farfetched to think that he's just going to use it for his own profit. So to keep that from happening this 2nd spirit had the ability to easily take away bending powers and was quite resilient against bending itself. With other words it was to keep the balance in check.
However because after a while, when the Avatar had been reincarnated so many times, he eventually was kept at bay by its own previous lives, making the 2nd spirit not needed anymore and forgotten. But this spirit too kept on reincarnating and eventually in this generation became Amon, who somehow realized his powers due to the trauma of losing his family.
...wot? Just a really wild theory for the fun xd
Putting aside the fact that Aang's spirit has been aiding Korra this entire time while she was fighting Amon and the fact that it makes no sense whatsoever that an avatar who saved the world, protected Republic City and has a no-kill and only-fight-as-last-possible resort policy?
So many questions about him..
