Don't be a jerk
Don't be a dick. If people abided by this, we wouldn't need any other policies. This is a corollary of ignore all rules.
"Don't be a dick" is the fundamental rule of all social spaces. Every other policy for getting along is a special case of it. Although nobody, including the Arbitration Committee, is empowered to ban or block somebody for being a dick, it is still a bad idea to be one.
No definition of being a dick has been provided. This is deliberate. If a significant number of reasonable people suggest, whether bluntly or politely, that you are being a dick, the odds are good that you are not entirely in the right.