I guess I don't have a formal proof for you, but in general the more characters/words a response contains the more significant, relevant, important, consequential, telling or material it is. Of course you can find counter examples, but considering the New York times still publishes articles and hasn't moved fully to Tweeting (yet anyway) I would say more often than not it's difficult to convey or articulate things correctly in 140 characters.

If a communication method is "low-stakes,informal and brief" how often do you expect to be meaningful? To me those things are diametrically opposed to me.