Socialtext implements printing via a CSS file for print media. A wiki page has the following link in the header:
<link rel="stylesheet" type="text/css" href="/static/.../css/st/print.css" media="print" />
This CSS file is applied when the page is printed. This saves a trip out to the server for a 'printable' version. The CSS file hides all the non-text parts of the page. If you wish to have a different look for printed pages, you will need to update this CSS file.