Add the formating rules to the end of each page. This is pulled in from a page itself. See [.TextFormattingRules] as an example. This way you can configure your support for the edit pages. I know this is pulling in two pages to deliver one page, but it makes it flexible and also a very small mod.
Here is another example of someone adding this kind of thing [WikiPatches/BetterEditPage]
--- wiki.1.0.0.pl Thu Sep 12 10:53:14 2002 +++ wikipatch.TextFormattingPatch.pl Tue Dec 23 12:24:34 2003 @@ -3300,6 +3300,9 @@ print "<h2>", T('Preview only, not yet saved'), "</h2>\n"; print '</div>'; } + &OpenPage(".TextFormattingRules"); + &OpenDefaultText(); + print &WikiToHTML($Text{'text'}); print '<div class=wikifooter>'; print &GetHistoryLink($id, T('View other revisions')) . "<br>\n"; print &GetGotoBar($id);