Thread:Project:Support desk/Special characters (+ symbole) in url/reply (5)

Note $wgUsePathInfo should be auto-detected based on if your webserver supports it (or at least I thought it was. Maybe that has changed, maybe our auto-detection is just crappy). I'm kind of surprised that changing it has any affect in this situation.

I believe this issue can also sometimes be caused by using the wrong flags in a rewriteRule clause in a .htaccess file.