I don't like that concept of essentially inlining styles in the class attribute. It is just a misuse of html classes.
Class names should be used sparingly and describe the semantics of an element rather than its visual appearance. It should be something like class="button submit disabled" instead of class="f6 link dim br1 ph3 pv2 mb2 dib white bg-black".
If anything these styles should be exposed as sass mix-ins that you can use in your own styles. So you have a named set of style mix-ins that do not pollute class names.
Class names should be used sparingly and describe the semantics of an element rather than its visual appearance. It should be something like class="button submit disabled" instead of class="f6 link dim br1 ph3 pv2 mb2 dib white bg-black".
If anything these styles should be exposed as sass mix-ins that you can use in your own styles. So you have a named set of style mix-ins that do not pollute class names.