The problem is that the collapse is on the right. It used to be this way on Reddit too, but after users complained they moved it to the left. Right now it's hard to collapse a series of top level comments in a row since you have to keep moving the mouse around a lot.
Feature request to move the collapse to the left side, like on reddit?
The one thing the web should have had from the beginning: flexibility of what happens to the contents on the client. Somehow this "feels right", given the original Alan Kay's vision of what should be happening on a personal device. Users should always be able to tweak things the way they like them.
Feature request to move the collapse to the left side, like on reddit?