Maybe there's a sample bias because of the online communities I visit (like HN) and the real world that I live in, but in general, I've observed that people in real life seem overly concerned about keeping things "harmonious", with all the small-talk, the lack of real listening, talking past each other, not voicing differing perspectives, etc. They also seem to lack patience in various things, whether that's discussing or examining something (can't think of examples right now), and would rather "go back to their own lives". In contrast people online seem so much more generous.
I'm guessing this is partially because "being on the internet" naturally filters people. But what else is there? What's your experience with people online vs in real life? Why do you think this is the case?