There are rules the community follows to maintain a certain level of social cohesion, which in turn aides us in the pursuit of rationality.

How is that demonstrated?

Those rules are rarely discussed outright, at least not comprehensively.

I'm pretty sure if I started posting half of my comments in pig-Latin or French or something, for no apparent reason, and refused to explain or stop, I'd be asked to leave fairly quickly, though. That all communication will be in plain English unless there's a reason for it not to be is one example. I'm sure there are others.