Your question is a false dichotomy. The FAQs aren't the FM for a user interface, they are the FM of a community of humans. The mechanics of the UI are, in fact, about as self-explanatory as any web site is likely to be. The issues of topicality, civility, &cetra are self-explanatory insofar as anyone who watches the site for a few days will see them all in action -- but most would consider it cruel to remove the extended explanation.

Your question is a false dichotomy. The FAQs aren't the "FM" for a user interface, they are the FM of a community of humans. The mechanics of the UI are, in fact, about as self-explanatory as any web site is likely to be. The issues of topicality, civility, etc. are self-explanatory insofar as anyone who watches the site for a few days will see them all in action—but most would consider it cruel to remove the extended explanation altogether.