Just looking at the ifauth plugin it seems like it will sort of do what I want. I use dokuwiki to store AD&D game information. I have some pages with player info and some with DM-only info. ACLs can be used to control who can see which pages, but making references to the DM information is awkward. One way is to put DM footnote indicators in the general page, and then keep the notes in a separate protected page. But then the players can see what things have footnotes. My other solution is to maintain two copies of a page -- one with DM notes marked in Bold and one without. This means maintaining changes in both copies. It looks like ifauth could be used to hide the notes as follows:
The innkeeper lives in a small room at the back. <ifauth @DM>(DM note: he's a vampire)</ifauth>
Users in the DM group would see: "The innkeeper lives in a small room at the back. (DM note: he's a vampire)"
while other users would see only: "The innkeeper lives in a small room at the back."
A nice enhancement would be if the privileged information could automatically be formatted in a certain way to indicate that it is privileged, for example by background shading. Of course the formatting could be done within the ifauth tag, but being able to specify the format once instead of having to code it every time would be a lot more usable.