Yeah this one seems absolutely insane, how many Satoshi Nakamotos are there in the world? It's very plausible to see the name on a mailbox (or meet the person) and think "that'd be a cool handle." And it's so wildly improbable that someone else would make up exactly the name of a neighbor of one of a small clique of obscure internet cypherpunks. It's not like the name was "John Smith" or anything.

But I don't know how to square that with the "Finney was running a marathon while satoshi sent emails" claim.

Given Back and Finney's close-ish relationship, that same fact could have permeated to Back, and would be a further reason for him to use the name. That said, it's all pure speculation so :shrug:?.

Is it a coincidence? Or is it really bad opsec from someone who was otherwise pretty good at it? Or was it really good opsec and someone wanted to plant little clues that it was finney?