[geelen]

Well, the problem with having foo and foo--bar but not both is that contextual overrides become a problem. Having both of them solves that but clutters things up.

This is a technique to better express your styling intent through markup. Instead of <div class="x x-y z"> you have <div x="y" z> - two namespaces instead of one.

[shadowmint]

So its to avoid human readable visual clutter?

...by having obscure custom attributes?

That seems extremely close to having size="big" and color="red" from html4.

How is this not just going back to a known bad design pattern?

[lowboy]

It's trying to ease the problems surrounding contextual overrides.

Having color="red" and other inline styles is a bad design pattern, but AM only superficially resembles it in that it uses attributes. Whether you give an element the attribute of class="nav" or just am-nav, it's accomplishing the same thing: defining that it's a "nav" element for purposes of styling.

[masklinn]

Not to be insulting but… are you unable to read text? Because the problem (which has nothing to do with visual clutter and has to do with modularity and contextual overrides) is explained from the third section "Contextual overrides".