Requiring a commentary might help - but commentaries might be short in order to be first.
Adding a commentary can take time to do it well. Plus, if you're making an effort to make an article easier to read a user might have:
  • copy/pasted an article as a discussion
  • added images via links from the original
  • hyperlinked references within article
  • added bold, italics, headers and the original link
I know, because I've done this myself several times only to find that others have posted this, or a similar story from another source sometimes as a link and sometimes with commentary.
I don't really mind spending the time doing this I've time and the sats aren't the point. Often I've got my own reward because I've spent so much time on the article I've understood it far more.
Not sure how to implement some sort of POW, or even if its worth it, but I though I'd put my two sats in.