Ben Model is a musician who accompanies silent movies as well as a silent film historian. He's done some very interesting work taking silent comedies and demonstrating the difference between the speed at which they were originally projected and being projected at a realistic speed.
It was standard in the silent era for films, and comedies in particular, to be undercranked. What that means is that if the film was going to be projected at 16 frames per second, it would be shot at 12 frames per second so that when projected, the images would be faster than life. The term "undercranking" comes from the fact that cameras were literally cranked by hand.
There was no fixed projection speed during the silent era. Projection ranged anywhere from 16 to more than 24 frames per second. Initially, projectors were also hand cranked, but even when they were motorized, they were controlled by rheostats which could vary the speed within a single film.
What's interesting in Model's examples, is how the actors adjusted their speeds so that they would get the desired result on screen. Here is the boxing sequence from City Lights (1931). At this point in time, film projection had been standardized at 24 fps and cameras were motorized due to the need to synchronize with sound. Chaplin still preferred to shoot with an older camera so that he could continue to use silent comedy timing.
There are differences that Model points out. Characters seem to weigh less when in fast motion. This lends a sense of unreality to the physical knock-about that allows it to be funny. When Buster Keaton and Harold Lloyd made sound films in the 1930s, their falls appeared painful because they were accompanied by sounds of impact but also because being timed realistically, they looked like real people hitting the ground and the audience viscerally felt the impact.
The speed itself adds comedy to this fight. In real time, it's leaden, but sped up it has a lot more energy.
One thing that the extra speed required was increased clarity. With gestures faster than normal, it was important to do only one thing at a time so that the audience could read the actions clearly and not get confused. In this Model version of a clip from The Adventurer (1917), pay attention to Chaplin and the empty glass in his hands. When the drink is finished, he licks his fingers, puts his fingers in the empty glass and them licks them again and drinks from the empty glass, hoping to find a final drop. There's the rule of threes in operation; Chaplin performs three actions to show that he wants more, but hasn't any. That's all an anticipation of the gag where he tips another man's glass and steal the liquid from it.
Model has other examples available here, including one from Sherlock Junior (1924), starring Keaton. In Chaplin's last silent, Modern Times (1936), he sang a nonsense song at the end, which forced him to shoot at 24 fps. However, before, during and after the song, he cut in undercranked footage shot with a silent camera. Note how different the speed of people's motions are in the two types of footage. While Chaplin's song is funny, it's like he's stepped into a different world where everything is sluggish by comparison. I should note that this clip contains the last verse of the song, one which Chaplin edited out for re-issues and is missing from the latest DVD release of the film.
The animators and directors of the 1930s and '40s grew up watching silent comedies and absorbed the feeling for fast action. Bobe Cannon's smears in The Dover Boys are 4 frames long. Tex Avery talked about bringing in an object 4 frames before it beaned a character. Rod Scribner's animation has the broad energy of silent comedy. The furious anticipations that animated characters go through before zipping off screen owe a debt to the sense of speed that silent comedy introduced. Animation caricatured it, pushing it even further. Fast is funny, especially when it's been combined with movements that read clearly.