Yeah, restraint is not a bad thing, especially at the movies, but to the point where you have to rein in spontaneous reactions? Spontaneous (verbal) reactions from the audience actually help to improve the atmosphere.

Of course, expressing yourself so freely to the point where you seriously disturb other people, like the examples you've mentioned is not a good thing. That drunk guy urinating in the corner is just... *urgh*

Boy, are the Japanese in for a shock if they watch a movie at an American theatre ;p

Ching Kin Min
Japanese Culture