I like to use M-h in Emacs to mark paragraphs. I also like to use the Command key as Meta. Further, I like to use ⌘H to hide applications in OS X.
If you hit M-h in Emacs, it runs mark-paragraph, which is good, but means that you can’t hide Emacs. However, if you hit ⌘tab to trigger the app switcher, then select Emacs, then hit ⌘H, it will hide instead.
Alternately, you could bind ns-do-hide-emacs to some other key combination.
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