Voyager

Boost also had this handy feature where you could tap a button to see the parent comment. It would open a popup/modal window displaying the comment with the usual updoot/downdoot, quote/reply and parent buttons - so you could easily repeat the process and read the parent context up to the root.

That was handy in long complex threads.

As a work around, you can tap on the comment to hide its children, or if you swipe to the left it will collapse the entire thread.