You can find the full source code for this website in the Seam package in the directory /examples/wiki. It is licensed under the LGPL.
Facelets by default ignores comments when building the JSF component tree, put this in your web.xml to enable comments:
<context-param> <param-name>facelets.SKIP_COMMENTS</param-name> <param-value>true</param-value> </context-param>
(The Facelets documentation says it is true by default, but it turns out that this is (often) not the case.)
See this FAQ entry to find out an alternate way to comment out blocks of markup in Facelets.