Definitely felt a little off, but if I didn't know that this was a deepfake, I would probably accept it as real. As usual, I don't know if that fits more in to the "remarkable" or "disturbing" category.
Eh, I'm not entirely sure I would have. The effect is near identical to when you have one person behind another, pretending to be the front person's arms and hands - the motions just don't match up right.
Maybe people who use faces more than full body language are more affected by this particular one?
I kind of agree, but it's hard to separate knowing that it's fake from my reaction to it. If this were presented without that context, I might feel like it's off, but not necessarily question it, especially if it came from a source I believed to be legitimate.
I also think, on top of all your points (which I agree with), keeping it shorter would make it more convincing. I think with the current usage of social media, short clips created through some synthetic means will be harder and harder to identify.
Maybe people who use faces more than full body language are more affected by this particular one?