I guess I'd answer the question with a cui bono question. Why would someone of Paul Graham's standing need to fake this? What would be his incentive to do so? He has nothing to gain from faking it. And I can't think of anyone else who stands to gain, either.
Occam's Razor explanation is that he just thought it would be cool to show.
Without the link from his own site we can't tell who even claims to have done the typing. Someone who isn't PG may have all sorts of reasons to fake it. Gentle suggestion - if you think the answer to someone's comment is obvious then it's a good sign there's a miscommunication and you should consider other interpretations.
"Gentle suggestion - if you think the answer to someone's comment is obvious then it's a good sign there's a miscommunication and you should consider other interpretations."
To the contrary, I didn't think the answer to his comment was obvious. I don't claim to have the correct answer. And if that's the tone my comment conveyed, i.e., a dismissive one, then I probably conveyed myself improperly. That was not my intent.
Occam's Razor explanation is that he just thought it would be cool to show.