As demonstrated several times over, the content of communications barely matters when determining the identity of a leaker. Simply proving that a communication occurred between a source and a journalist prior to the publication of a story/package is often enough to see the source identified, fired or arrested. In some countries the identification of a journalist's source can even result in their torture and murder.

In other words, the general context of the communication can almost always be inferred from the "metadata", which is information about a communication, not the content of the communication.