I consider this definitive evidence that the foundational period of hacker culture was before these books were published. I'm not sure what the point of trying to shift that period forward so as to include Dennett's works is. It's neither true nor necessary.
His first three books were published in 81, 84 and 86.
I agree with you that the foundational period slightly predates these, but I don't consider the foundational period to be the same as when "hacker culture was established".
I began to encounter it myself starting in about 1979 via CoEvolution Quarterly/Whole Earth Review, but it was still very, very much evolving and continued to do so in very noticeable ways as I started programming in 1984.
I tend to consider the general use of IP as probably one of the main signifiers of hacker culture being established, and that was far from common in the 75-85 period (though growing rapidly).
It wasn't actually my claim that Dennett had much influence on hacker culture. I was originally disputing the idea that Dennett became well known after 1992.
Jargon file was published as The Hacker's Dictionary in 1983 https://en.wikipedia.org/wiki/Jargon_File
I consider this definitive evidence that the foundational period of hacker culture was before these books were published. I'm not sure what the point of trying to shift that period forward so as to include Dennett's works is. It's neither true nor necessary.