I have been following the recent block size debates through the mailing list. .....
Satoshi Nakamoto
I had not seen that letter until now, but it looks like a lot of vague bla-bla without even a hint of a technical argument.
I'll eat my hat if that was written by any of the very skilled mathematician/cryptographer(s) that designed bitcoin.
That letter is fake. It was not know at the time, but Satoshi's mail account has been taken over -- no one knows how or when. That was proved last September, when "Satoshi" sent a dox extorsion email from that address to some prominent bitcoiner.
Anyway, the phrase "in the face of widespread technical criticism and through the use of populist tactics" is a dead giveaway of its source. I only cannot guess who wrote it because there are several people at Blockstream, and many more among its supporters, who would have used those words, would not have any scruples in sending a forged message to support their agenda, and are naive enough to think that the trick would work.
The second paragraph, moreover, is totally at odds with the very idea that makes the protocol work.
Satoshi's writing and that particular letter have something in common: Two spaces after a sentence ends. That's the "old" way of writing in the typewriter era where you hit space twice - and you carry over that habit to the PC keyb into the late 80s/90s. You do it too because you are of the "old guard". Younger people, hackers, script-kiddies, well... not only don't they know these things but they won't even spot the difference in order to emulate it. The two spaces, for me, increases the chance that it was original. As for IPs, mail spoofs, hacked accounts, I can't tell you who controls what. The writing style is quite neutral and it feels ok'ish though and in line with what Satoshi has said in the past.
As for blockstream people doing it, you are saying that they hacked Satoshi accounts back when it happened and then they used them when convenient to promote their agenda? And how would they know that Satoshi wouldn't pull the curtain on them? Especially after Satoshi came out and said he is not Dorian? It's a very long leap.