In addition to what everyone else said, I think there are people who aren't shy or socially anxious, but who just don't do a lot of gushing. They can be having a really good time, but it doesn't show much because they don't express it really strongly. I think strangers might find it offputting, but people who are around them a lot can usually tell when they're having fun just as easily as they would everyone else.

(Personally, I have no setting between "FUCK YEAH!" and just kind of sitting there happily while people who don't know me well say "are ya booooooored? D:" every three seconds.)

Then again, they didn't say thanks, so they might just be a regular old douche. :/