Sure, but that influence has not exactly been positive. That's the catch I think. It's much easier to exert negative influence than positive influence.
It’s not that simple. Tribalism is easy and most considered a net negative. Tribalism is easy to sell because it’s ingrained in humans. That’s what 4chan does, pick the lowest hanging fruit.
It does but that’s not what a large scale scalable corp is trying to achieve. You want as many participants as possible enjoying themselves for as long as possible.
Maybe that's the key... sites should not become so large that it creates big echo chambers for one person to reach millions, it keeps other people having to search for answers and do their own research instead of just everyone listening to the same group of idiots.
Perhaps you could also force a limit on how much time was spent (or how many posts made in X time) on the site.