If leaking internal news/information, it should seem like a trivial exercise to disseminate an email with subtle unique identifiers in it and fire leakers.
https://en.wikipedia.org/wiki/Reality_Winner#Role_of_The_Int...
The lesson to take away is that metadata of all kinds is powerful. Even if The Intercept had just provided paraphrases to the NSA it might have still given away Reality Winner's identity.