Just a bit from ATP #14: "I'm terrified of doing anything that would make me look like a jerk in front of my family and friends"
That just doesn't seem true. He consistently goes out of his way to engage in trivial arguments with people, especially on Twitter. Literally days after the sale, he called out Anil Dash in a needlessly confrontational way about some minute error in his history of Tumblr (http://dashes.com/anil/2013/05/seven-years-ago-my-wife.html). Not to mention the time when got in some squabble with a writer for one of the Apple rumor sites, then blacklisted said site from every Instapaper account.
As far as I'm concerned, he's made a jerk of himself in public innumerable times already. He just seems like an abrasive guy. That's not to say that his work is inferior (certainly assholes have created incredible work before), but any fear of looking like a jerk is moot. He has been a jerk forever.
One thing is to write angry tweets, and in a very different level, would have been shutting it (or Instapaper) down just because he's burned out. He cares about his users.