Ask HN: Why no foldable threads on HN?

Dunno if it's just me but I feel like navigating from a thread to another is a pain, since they just indent over and over and lower and lower, and keeping track of indentation to associate a reply with its parent is no fun.

Has someone implemented such a feature already? Even read-only I feel like that could be a little useful. I wouldn't mind building it if no one has done so already.