No actually I was thinking of something similar the other day:
You could express the dependency we have on sound, and find a way to totally silence a character after some incident and the emotional impact and how the world is totally different in silence ?
Also you could do something whereby you place audio channels in one layer, and then have it playing, and subtitle different text underneath, a sort of "what s/he says, what s/he thinks" kinda concept
Another thing could be merely cutting out random words or silence in specific parts to evoke a sense of loss, or to purposely manipulate a story to lack a certain word/quality and then reflect it later on ? (kinda like the 'censoring' in Kill Bill 1 of Uma's name)
(edit)
On the point of captions, you'd need to justify just why you want to use it, why its in, the formatting, etc.