Not to snark him, but errh…sounds as if he did not carefully plan out his departure strategy.
If he’s threatening the well-being of the community by backdooring his activities for getting users to grok his fork then I do suggest confronting him about it. He may get tired in the long run but overall one should consider how other members are dealing with it and their own feelings on the subject which can hurt everyone in that longer run. Possibly a bump in the road or something greater. At most, you can tag him for spamming, if he’s getting people to jump ship, or make that attempt.
From your edits, he sounds like an intellectual bully. I wrote some pieces on here I plan to blog in the coming weeks from someone else’s account of dealing with this kinda thing. Good luck.