Ok, I've juste discovered that in the html5 specification you can omit tags. I've always been reluctant to push Jade to my coworker but it makes much more sense now.
This was legal for ages. Why do people think this is HTML5 feature?
This http://rimantas.com/bits/minimal_html.html dates back to 2005, but of course it was possible well before that.
Sidenote: "jade" is not a thing anymore. For legal reasons that no one understands but are in the past, the thing you're thinking of is called "pug", and lives on https://pugjs.org
