Shouldn't be difficult to build a tool to randomly obfuscate writing you want to conceal. Swapping words/sentences with semantic equivalents should be a rather trivial exercise. If the tool allows the human to revise and tune it, it's even easier.
I'd assume they had a (small) pool of candidates to start with and finding the author of texts in the group of authors is very far from identifying every person on Earth by linguistic style (as the article states)
Based on my conversation I got the impression (never confirmed) that he might have been more than one person.
I've always thought this as well. It really makes the most sense.
Um, unsourced speculation from someone with no credibility in the field making an allegation which on its face doesn't add up?
Why is this even here?