According to the article, the NSA compared Satoshi’s writings with trillions of writings across the internet. Creating a Satoshi fingerprint they were able to match this up with other writing fingerprints (using the power of a supercomputer of course) and bingo, they were able to unmask Nakamoto.
Technology moves fast these days and as soon as one back door closes another one opens up. So the NSA appear to be able to trace people by their own words and some are not happy about this. Cue the “Document Anonymization Tool” a GitHub project that does what it says on the tin. I’m interested to see where all this goes.