Thor´s hand being cut off is funny. He won´t go all Aquaman so it´s either
that Loki made an illusion to fool Malekith into trusting him of being "evil"/not on Thor´s side. I mean Loki does appear to arrive with this hands tied to that ship in the desert?
Or it´s true but there is a way to restore the hand with "magic".
I too think he will fool everyone. He might help Thor and take down Malekith but as Loki 882 and Dasher10 said, he will put himself in a position of power in the end.
I think it's neither. Loki I think is working with both sides.
That scene, with the hand cutting off, it was very, dream-like.
I will keep saying this until we see the movie, but I don't think it's an illusion, I think it is something that is "going to happen", but doesn't.
I think it's a vision of the future by Heimdal. Or a vision by someone.
It makes sense. Loki obviously has intentions to betray Thor, but the result would be his own death, however, he probably needs to align himself with Malekith also. Loki cutting off Thor's hand, is something that will lead to bad things for him. Which is why I think that he DOES play a part in attempting to offer Jane up to Malekith, but he deceives Thor, and makes it look like it was all Malekith.
Tom hinted at Loki slipping in between the cracks. He gets what he wants, and it works to his advantage. He gives up Jane to Malekith, but still manages to stay in Thor's good grace