Actually it does already :) - just double click the header bar in a comment (where the username is) and it will collapse that comment and all nested ones under it.
Would love to add a feature where if you swipe left, all the comments in that thread get collapsed.
It's useful when there are long threads that gets totally out of hand and you dont realize it until you're 1/3 way through. This way you can collapse all of them without having to go to the top.
