An old American tradition to not run a primary during a President’s second term who is running for office. I guess it’s supposed to help unify the party behind a proven winner or something. That’s mostly it. Liberals love traditions, guidelines, and rules more than anyone.
And even if you’re don’t get banned, just like Reddit, you may get down voted a lot if you go against the discourse of the current thread. But not sure if that’s fixable anywhere with big groups of people.