Last modified: 2007-12-31 11:20:32 UTC
Attempting to directly load a page with an interwiki prefix fails with an 'unsupported character' error, while directly loading an interlanguage page works as expected. Example:
This link works: http://en.wikipedia.org/w/index.php?title=fr:Main_page
This link does not work: http://en.wikipedia.org/w/index.php?title=mw:Main_page
Both titles work identically when typed into the search box; it's only when they are typed directly into the URL that the difference is noticeable.
The behavior appears to come from line 152 of Wiki.php, where a test for local interwikis is used to prevent redirect loops. Also possibly related to bug 850 (thanks to Splarkla on IRC for help with this).
This behavior is intended. Interwiki prefixes defined as local in the interwiki table display the behavior you demonstrated on fr: , non-local prefixes behave like mw: does. See also the blurb on iw_local at http://www.mediawiki.org/wiki/Interwiki_table