Talking over narrations on rides or pre-shows really gets under my skin. It tends to come mostly from people who are either unfamiliar with Disney or more often, English.
I've found that while this occurs with a fair amount of frequency at DL, it's much much worse at WDW, especially with tour groups from foreign countries. I don't think I'd go to a movie theater overseas and start chatting with my friend because I didn't speak the language - I don't understand why I need to hear loud conversations on the COP.
Interestingly, during my only visit to Tokyo DL (so far), I noticed that while the crowds could get manic - when a character appeared for a (cell phone) photo op, for example - the people waiting in queue for attractions tended to be respectful of one another. I'm sure that part of it has to do with the fact that pretty much everyone at the park spoke the same language. Also, people there seemed to really dress up to spend a day at the park, as if they were going to a nice restaurant or the theater - I'd love for that attitude to return to the parks in the US.