Collapsible comments (user script)
In my opinion, large threads with many comments can be pretty difficult to navigate. Ideally it would be natively supported by Duolingo, but for now I've developed a user script that makes (sub)threads of comments collapsible.
Here is a screenshot to illustrate it: https://files.degeberg.com/userscripts/duolingo/comment_collapse.png
Simply click the little minus/plus button on the right to collapse/expand a thread.
The userscript can be downloaded here: https://files.degeberg.com/userscripts/duolingo/comment_collapse.user.js
Bug reports and suggestions for improvements are of course welcome.
PS: You may also be interested in the new comment indication user script.