now, this seems like a foolish assertion on your part.
Norms are established through similar processes in many different environments.
There is no implication that every action is either prohibited or mandated.
There is an implication that some behaviors are preferred to others.
Why that translates to a universal conclusion, i'll never know and you'll never prove.
And why one can't believe that the authorities here (kori and timvp) have some actions that they prohibit and others that they prefer don't occur but won't always prevent or impose consequences upon violators is a complete mystery. Based upon the faqs, they - the authorities prefer (and many users prefer) that this type of thread not be started.
And within a hierarchical structure, there is a formal authority often and then there are group norms which are established. These norms aren't rules with consequences, but standards of behavior that members prefer, recommend and encourage.