"I have written software ... (which would be) ... a neat way for users to find old threads. HN's archives are rich."
To serve us till such time as the software which dang mentions becomes available to us, I created a new subreddit for discovering and sharing great content (comments and discussion threads) from the rich HN archive:
http://www.reddit.com/r/bestofhn/
I have seeded the subreddit with a few discussions from the past which I found interesting. Do take a look!