But how? Tarrlok's bending has been taken away and same with Yakone. Unless Yakone somehow is Amon and got his bending back. I doubt it though.
Amon is bloodbending.
Look at the clip again, you see Korra kneeling in place and doing that "bloodbending shake", and Mako is doing the same sort of shake, and yells "KORRA" in a normal voice, just like when Tarlokk was bloodbending Korra and Yakone was bloodbending Aang and they were able to speak, but not move. Korra/Mako could've gotten up if they weren't being bloodbended. Only their hands were tied.
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_foolmo_
'nice comma splice' - TomNook7