Brillant stuff, Rémi! I have applied them in one of my HTML emails I’m making and I’m certainly happy I did. And if it wasn’t for you I may never get try the HTML5 doctype in my mails, I was surprised how it well it works.
I have a concern though, like others, I can’t get them working on mobile Google App, too. (I’ve tried testing your code as well but didn’t work either.) I’ve tested them on Litmus too, on Android 4.4 Gmail App. Woudn’t still remove the Fabulous Four though! ;)