Comment by tripzilch

You don't use Reddit do you?

They use a very simple system, collapsing posts after a certain depth, and hiding more comments after a certain number (10, I believe) at the level below the top comment (sorted by score obviously).

It works extremely well, and thanks to the fast JS collapsing, it's not at all a hassle to read a subthread that happened to get collapsed if it piques your interest.

It's so simple it may easily be overlooked in its obviousness, but really you don't need a very complex system that is strictly a lot better than no collapsing at all.