I don't know what he is referring to, either. He probably means this forum thread:
http://forum.dokuwiki.org/thread/3614. But that can hardly be called "documentation" and does not explain his behaviour. :huh:
These are not completely what you asked for, but could work as a work-around:
*
http://www.dokuwiki.org/plugin:userhomepage
*
http://www.dokuwiki.org/plugin:ifauth
*
http://www.dokuwiki.org/plugin:permissionstyles