[krapp]

Hacker News has a weird cultural dissonance where it's designed to encourage tangential conversations as you mention, but also has numerous features designed to discourage engagement and casual style for the sake of maintaining quality and avoiding the Eternal September effect. It wants to be a water cooler or a pub where people discuss interesting things, but no one polices the conversations in a pub or around a water cooler for topicality, novelty or substance.

It really should use a flat format to that end, but it's written in a lisp, so not having it render a tree view is probably sacrilege.