I don't buy any argument saying that an FAI must be able to modify its own code in order to take off. Computer programs that can't modify their own code can be Turing-complete; adding self-modification doesn't add anything to Turing-completeness.
That said, I do kind of buy this argument about how if an AI is allowed to write and execute arbitrary code, that's kind of like self-modification. I think there may be important differences.
It makes sense to say that a computer language is Turing-complete.
It doesn't make sense to say that a computer program is Turing-complete.
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