Late Saturday, the Times revealed that Trump had declared a $916 million loss in 1995, wiping out any federal taxes that year and setting himself up to avoid 18 years of similar obligations. The Times’ story was a rare animal, a bombshell based on a source whose identity is unknown even to people at the news organization that broke the story. Although anonymous sources are commonly used by journalists to elicit sensitive information, reporters almost always know their identity, even if they don’t disclose their names to readers or viewers. That doesn’t appear to be the case in the Times’...