Last modified: 2014-02-12 23:53:50 UTC
http://en.wikipedia.org/wiki/?mobileaction=opt_in_mobile_site ^ that URL shows mobile format in your browser, but after submitting you go to the regular desktop view. At least this is the case on a browser that doesn't auto-redirect due to not being a recognized mobile device or having set that 'disable' cookie which can't be unset.
This is no longer happening. I believe Arthur Richards did some work around this so closing. (Arthur please provide relevant commit if you can)