I was only ever a regular on the (small, now-defunct) irreality.me imageboard. The most activity I ever performed on 4chan was that time I wrote a bot that responded to every post on /pol/ with a random section of Society of the Spectacle (in an arguably successful attempt to improve the quality of discussion there).

I find imageboards to be interesting from a media-studies perspective, though. They're a clear case (even clearer than twitter) of design influencing user behavior in a way that eventually generalizes outside of the platform. Three countries have shockingly similar & arguably totally distinct right-wing authoritarian populist movements that sprung up from totally distinct popular imageboards during the same period, & there are probably more that I'm simply not aware of. So, serious study of the kinds of behaviors imageboards encourage & highlight (and serious study of under what conditions those behaviors generalize) is potentially really interesting. It's one of those things that makes me wish I was a real social scientist instead of just a programmer with hobbies.