INTERNAL code in WYSIWYG is not passed off to wiki parser
When adding | INTERNAL ] code to an url while using the WYSIWYG mode, vBulletin doesn't pass it off to the wiki parser and assumes the whole thing is the URL. It then adds a bunch of code all over the place.
For example:
[URL=http://www.my-forum.com/photopost/showgallery.php?cat=519|INTERNAL]
becomes:
[URL="http://http://www.my-forum.com/photopost/showgallery.php?cat=519%7CINTERNAL"]