Group dynamics observes how people behave in groups.
Drop any group of people into a confined space (or cube!) and similar patterns begin to emerge.
There will be leaders, followers, and dissenters.
People wil become friends, lovers, frenemies and outright enemies based upon external stimuli (more than individual character traits).
This is mostly true of communities as well. You can't stamp out all fights simply because it's part of ingrained group dynamics.
More importantly though, you can worry a little less about removing a key member or asking a 'too active' member to post a little less. If they leave, or are removed, it creates a void for other people to fill. And other people will fill the role.
If you remove the mild troll everyone knows, you might well attract another troll that you don't know.