Is there anything more subversive than humor? The sly eye let's us in on the fact that someone knows something but they're not saying what. Sometimes the front is taken to extremes, leading on or awry…But more often deadpan is a barometer of the real.
Let's make a few key distinctions. Keaton's deadpan was total, unlike the Cheshire face, of say, Jack Benny. Or the forced layback grimace of Bruce Willis, fake unflappable. Keaton's mien says everything because it reveals nothing.
And deadpan is not stoic, in the modern notion of strong silent unblinking internalizing. Deadpan is more like the original Greek Stoic ideal, if something cannot be changed, why worry?
In these days of Irony's death throes, when the macabre and unthinkable passes as nightly enfotainment - a detached countenance is countenanced as survival strategy. Not only does a good deadpan give cover, it preserves spirit, and speaks volumes at the same time.
Some last thoughts; the gaze of a Keaton is earned, it doesn't come easy. Use with caution, practice makes perfect. Don't mistake sangfroid for uncaring. A well placed take is a thing of beauty, and a joy to behold.