OK so this is really unintuitive, but while in the wiki there is a button labeled "Search" directly under the search box, it will take you here
http://wiki.xbmc.org/?title=Special:Search .
You have to click that then use the wiki only search box on that new page, and then you'll still get crappy results, but skinning did provide relevant results.
I tend to google "site:xbmc.org/[forum,wiki] searchterm" because the site's search fails all around (thanks to jmarshall who suggested google when I complained about the site's search engine in irc)
oh, thanks
works good. maybe get rid of the search box?
that is already added to my todolist on the site, once I get some real life out of the way