Sorry, but the need to put "<!-- -->" everywhere is a dealbreaker for me.

Example:

  <div class="grid__item  lap--one-half  desk--two-thirds">
      ...
  </div><!--

  --><div class="grid__item  lap--one-half  desk--one-third">
      ...
  </div>

What's the rationale for using inline-block instead of float?