I know css-box hasn't been touched for years, but collapsing margins keep haunting developers, even to this day :-P

In particular people don't like the fact that margins are collapsed also between child and parent elements, as you surely know. So people resorted to overflow:hidden, transparent borders, 1px padding and other weird hacks.

Not everything doable with boxes is doable with flexbox and grids, like http://jsfiddle.net/noLyhwcj/ so maybe it's worth doing this?

Thank you.