tl;dr: I propose adding http://schema.org/subjectOf as a named reverse property of http://schema.org/about. The domain would be http://schema.org/Thing and the range would be http://schema.org/CreativeWork and http://schema.org/Event.

There are lots of cases where the main subject of given page is a Person, Organization, etc and authors want to mention there is a work about that entity. It would be nice to have a "subjectOf" property to link to the work. (In JSON-LD, you can use @reverse, but there is no reverse mechanism in microdata yet.)