I'm not so sure what this is trying to solve to be honest. I mean, in the example of David Walsh, you could just add a class to either div and be done, so why put inline styling (within a style element I mean) to get the same result?
Are there usecases for this?
What I can imagine though is that you can set the scope based on an internal anchor within the CSS, something like this (warning: pseudo code and weird attributes ;) )
<link href="styles.css" rel="stylesheet" scope-id="styles">
<div class="component">
<style scoped scope-anchor="styles#component"></style>
<!-- elements here -->
</div>
That way you can relate the used styles to a part of the stylesheet.
In that stylesheet you could have something like this (again: pseudo code):
@anchor components {
p {
color: red;
}
}
Anyway, just my brainfart for this morning ;)