Hi,
I'm using Emacs for mediawiki editing on a daily basis. mediawiki-mode
has a number of cool features including syntax highlighting, snippets,
quick moves, helpers for talk pages, ability to open, navigate and
publish without leaving the editor… And as it's not an editor designed
specifically for wikitext, you also have the extra benefit other modes
such as javascript or css.
There is no contextual auto-completion, though; ie, completion is only
based on what has already been typed before.
Best regards,
--
Jérémie