Originally Posted by SlackBrian
The thing that sticks out in my mind about that scene was the mocking tone Loki said "sentiment" with. I don't recall any tears, but I can't say for sure if there weren't any. But his tone and attitude didn't seem to suggest a conflicted nature about what he was doing.
Edit: Just watched the scene again. Yep, there was definitely a single tear that rolled down his cheek after he stabbed Thor and said "sentiment". So, hooray.
Yes, he mutters "sentiment" to himself in a sort of "that's adorable
" kind of way. In fact, I think Joss Whedon does like to employ characters muttering things like that to themselves. Iron Man says "tourist" referring to Thor, obviously "puny god." I would imagine it's something Whedon likes to do as it crops up several times in the film.