I can't find it right now, but it lead me to purchase the book "Permutation City" which is now one of my favourite novels because of the way it comings CS, philosophy, and writing that isn't stilted like a lot of the stuff you find in this realm.
The reason I can't find the comment is that there are pages and pages of them that mention Permutation City on Google. See for yourself, Google:
permutation city site:ycombinator.com
If you haven't already, then don't wait to buy the rest of Greg Egan's œuvre. It was "Quarantine", a lovely plot but arguably one of his weakest stories, that got me into his work, and since then I've found no-one except possibly Ted Chiang (whose work is very different) who comes anywhere near him in the world of hard sci-fi. Almost everything of his is rewarding, and I believe a lot of it was relatively recently (within the last 5 years or so) released as e-books after a long period of unavailability. He also has generous excerpts from selected books and stories at his web-site, and—my favourite—proves his non-fiction science bona fides as a regular contributor on the n-category Café (https://golem.ph.utexas.edu/cgi-bin/MT-3.0/mt-search.cgi?Inc...).
Oh, actually I did read The Business, which introduced me to the delightful question "how do you count to 1000 on your fingers?" (without using 'intermediate storage' like keeping track of 10's in your head). I still use that when teaching elementary number theory.
The story (https://qntm.org/responsibility) was really fun, and there were good comments too. It's certainly one of my favorite HN posts.
Re: OQ, I don't have a single favorite, but I like whenever the hivemind hashes out what's going on with a big tech issue, like Facebook's post denying complicity in NSA spying.
I've never read anything like Greg Egan. While reading 'Diaspora' I could feel my skull expanding - he pushes you to think at a magnitude we're not used to. The last few chapters of Diaspora are something I often read myself to bed.
https://news.ycombinator.com/item?id=12152658
It was this HN comment that prompted me to read it, fascinating book. The topic of the post, Boltzmann brain, is also well worth reading into.