Reddit posts often get one off-topic top level comment that spawns a huge subtree, but it's easy to deal with there because the uninterested reader can click the [-] button to collapse the whole mess. I wonder if HNers would stop viewing the NSA threads as such a problem if HN implemented comment collapsing.
There's a third party implementation of that (https://github.com/jaekwon/HNCollapse), but I that doesn't really help a commenting culture that is shaped by not having it built in. HN commenting threads are winner take all with respect to the top level comments. Once one gets entrenched the others die on the vine. To a lesser extent the same thing happens at subsidiary branches as well. It makes for a very unbalanced tree.
HN Collapse is an absolute must and should be implemented by default, IMO. Whenever I'm on a machine/tablet without it, my reading experience is much poorer.
