Earlier quoted context omitted.
Traditional forum style sorting just sorts for controversiality. Posts that generate heated discussion will continue to push their way to the top. This is okay but it means that non controversial stories will not make it to the top, which is honestly one of the largest benefits of news aggregator sites.
How about, here and on reddit, being able to mark threads you're interested in, and having a page where you can see those sorted by last reply. On HN, make that page refresh every 15 or 60 minutes or whatever. Heck, once every 24 hours would be enough... sometimes I just want to talk about the things that interest me, with the people that are interested in them. I would love to be able to think on something for a few…
To be honest, I think that a change in behavior needs to come from the website, top down, rather than allowing the community to opt in to an alternate scheme that will never hit the popularity threshold necessary to work. Like a sibling mentioned, Reddit has "newest", but because it's not on by default, no one bothers to use it.
I don't think that it's our attention spans that cause our browsing behaviors on aggregator sites- I think it's purely derived from the Ui/Ux of the site, and that if the site kept interesting conversations up longer, people would participate and have more than the surface-level reflexive remarks we see here. This is not just a hypothesis - we can see the alternate behavior born out on forum sites. I think it's a huge shame that HN has opted for this model (especially when it wants to be "the better news aggregator"). Think how many great conversations never happened here because the algorithm prematurely killed the thread - due to lack of upvotes or something else.