The wikit doesn't make it clear in HTTP mode (stand-alone or via
CGI) which encoding it uses. Witness the Tcl wiki where a number
of pages are delivered in Latin-1, while some are also delivered
in UTF-8.
The attached patch makes all channels use UTF-8. It also tags the
edit page as UTF-8 so that new input is taken in that encoding.

Thank you for the explanation and patch. I've applied it.