cross-posted from: https://feddit.org/post/9414466
See big red box on image attached (collapse as in the feature on reddit)
There is also a container feature already. I marked it at the bottom of attached image with a smaller red box
Not sure if this is what you mean or I'm being stupid, but if you step with your cursor over the username and time of the comment, it will highlight and you'll see a button with a minus icon on the right side - you can click that to collapse the comment
(Edit: I discovered this by myself after months of using this and thinking there was no way to collapse comments like in Reddit)