HTML::Template does not read files as utf-8, so modifying ikiwiki's template files to contain utf-8 won't currently work.
It seems that the best way to fix this would be to make HTML::Template support utf-8.
A workaround is to change all the template reading code like this:
- my $template=HTML::Template->new(blind_cache => 1,
- filename => "$config{templatedir}/page.tmpl");
+ open(TMPL, "<:utf8", "$config{templatedir}/page.tmpl");
+ my $template=HTML::Template->new(filehandle => *TMPL);
+ close(TMPL);
However, this will make ikiwiki slower when rebuilding a wiki, since it won't cache templates.
Could be approached by using HTML::Template's support for filters. Just make it use a filter that turns on utf-8
Or by subclassing it and overriding the _init_template method, though that's a bit uglier