User blog comment:Dopp/Technical Update: August 9, 2011/@comment-3080486-20110810114054/@comment-3388044-20110810135614

Go to Special:Preferences, go to the Editing tab, untick Enable Rich Text Editor. That takes care of it for you.

For the entire wiki, you first have to build a consensus that the majority of other members agree with you, and you need to develop a good argument as to why your wiki will function better without visual mode (i.e., RTE). Then you contact Staff using your wiki’s Special:Contact and present your case. Staff may, or may not, disable the RTE at your wiki.

Finally, on pages where use of the RTE messes things up, you can always place the magic word     at the top. This will cause anyone editing the page to have to edit it in source mode.