The performance impact might be just like 0.2% or something. But if we do as a principle remove 100 useless things that each are 0.2% that's 20%, so it's a policy of simplicity as much as anything else.

We could also drop this from HTML_HEAD.tpl:
<meta http-equiv="Content-Type" content="text/html; charset={$CHARSET*}" />

Discussion on http://compo.sr/forum/topicview/browse/deploying/dropping-non-utf8.htm

If we drop UTF8 we can drop some of the textcode symbols that Comcode supports, like the way to write a euro symbol in ISO-8859-1.

If we assume UTF-8 we can drop Comcode symbol shortcut syntax...

$shortcuts = array('(EUR-)' => '&euro;', '{f.}' => '&fnof;', '-|-' => '&dagger;', '=|=' => '&Dagger;', '{%o}' => '&permil;', '{~S}' => '&Scaron;', '{~Z}' => '&#x17D;', '(TM)' => '&trade;', '{~s}' => '&scaron;', '{~z}' => '&#x17E;', '{.Y.}' => '&Yuml;', '(c)' => '&copy;', '(r)' => '&reg;', '---' => '&mdash;', '-->' => '&rarr;', '<--' => '&larr;', '--' => '&ndash;', '...' => '&hellip;');

We'll keep the non-utf-8 support for now, but it'll be added as non-maintained in the maintenance system.

Some people may be integrating with legacy systems where iso-8859-1 is baked really deep into the content being managed.

Maybe it can be dropped in 20 years ;-).