i think that if you're captioning a film and you don't spell out all "foreign" words in their original language you should be drawn and quartered. the point of captions is that the textual information should match the audio information
to clarify in case i didn't make it obvious enough: i'm not saying all spoken dialogue should be translated. i'm saying the captions should accurately display the dialogue spoken, regardless of language. e.g.:
BOB: hello i am speaking english.
SARAH: hola estoy hablando español.
instead of the much more common
BOB: hello i am speaking english.
SARAH: [SPEAKING FOREIGN LANGUAGE]
