In LocalSettings.php put:
$wgLanguageCode='zh-tw';
$wgRightsUrl='http://GNU.../';
$wgRightsText='GFDL';
and select English in your user preferences, and view say the Main
Page of one's freshly installed wiki.

You will notice (best to test on a ISO-8859-1 console for full impact) how
MessagesZh_tw.php:'copyright' => '本站的全部文本內容在$1之條款下提供。',
does NOT change to
MessagesEn.php:'copyright' => 'Content is available under $1.',
despite the users preferences.

I looks like

Powered by MediaWiki

* This page was last modified 14:29, 30 November 2007.
* ????????????????????GFDL??????????????

Maybe this has to do with GlobalFunctions.php:

• Use this if the message should NOT change dependent on the
• language set in the user's preferences. This is the case for
• most text written into logs, as well as link targets (such as
• the name of the copyright policy page). Link titles, on the
• other hand, should be shown in the UI language.

But all I know is now on the bottom of every content page, a message
that could simply be in the same language as the user's preferences,
now becomes guaranteed gibberish if the user's language preference is
different than $wgLanguageCode of LocalSettings.php.

Or maybe the intention is "$wgLanguageCode will be written by the user
using the same language as $wgLanguageCode, so we dare not let the
surrounding text be in a different language." But you see above how
the net effect backfired.

Version: unspecified
Severity: minor