Wikimedia Bugzilla is closed!

If you want to have a group wiki where everyone shares some set of namespaces,
and don't want to allow for the main namespace to be writable by all -- for
instance, if you are concerned that people will misunderstand the use of
namespaces and post private material there -- it is difficult to do.  The
default setup allows removing permissions by namespace, but don't make it easy
to restrict the main namespace specially.