I guess the reason I never thought to write this is when I put a .txt file
in ikiwiki, I'm happy enough to see it copied through unchanged.

I guess the advantage of using this plugin is that you get the page wrapper
around the preformatted text, and could even inline such a page.

There is not currently a good way to turn off some processing steps for
some page types. It's either all or nothing. --[[Joey]]