I think it's satoshi himself. The way @satoshi and @saatoshi_rising break up their sentences is the same.
Looking at their posts, they both like to leave two spaces after a period.
@saatoshi_rising: "I am the creator" is also quite thought-provoking. Does it refer to the creator of the puzzle, or the creator of bitcoin?

Of course, this is just my guess.
Satoshi rarely used phrases like "by way of excuse" or "what is especially embarrassing." or "I will make up for two years of stupidity". There is no cryptographic signature or undeniable link to Satoshi unless proven otherwise. Probably not Satoshi. But who knows? He could be anyone (a pseudonym) here… or no one at all.