How about a plugin adding a
-[[preprocessor_directive|preprocessordirective]] to render some given LaTeX
+[[preprocessor_directive|ikiwiki/preprocessordirective]] to render some given LaTeX
and include it in the page? This could either render the LaTeX as a PNG via
[[debpkg dvipng]] and include the resulting image in the page, or perhaps
render via [HeVeA](http://pauillac.inria.fr/~maranget/hevea/index.html),