Thread:Extension talk:WYSIWYG/IE11 with MW 1.22.0 + WYSIWYG extension: Existing category definitions will corrupt after after page has been saved/reply (11)

Inserting as the first metatag in the page (I don't know how to do this in MediaWiki, sorry) should force IE11 to Compatibility Mode.

Maybe the devs at Wikia/WYSIWYG weren't aware of this workaround. If we succeed inserting the metatag on "wgAction=edit" only, we'll solve many problems at once.