On Mac OS X El Capitan, a menu item titled "Enter Full Screen" is automagically being added to the application's "View" menu. This item is not present in earlier version of Mac OS X.

You can see this bug in Atom—on El Capitan, Atom's "Toggle Full Screen" option is shown in the View menu, and a mysterious extra "Enter Full Screen" item is listed at the bottom. Both of them actually do work.

I like the idea proposed in #2811 of having the full screen mode handled automatically, but this behavior needs to be consistent across platforms and OS versions.