We've had an experimental method of avoiding deeply nested comment threads in effect for a little over a week now, and while I think it's useful in some ways, it's definitely also pretty confusing in some cases (as multiple people have pointed out to me).
I've made two changes to it now that should help quite a bit:
The flattening will now only happen when there won't be any "sibling" comments after the flattened thread.
This is to avoid what seemed to be the most confusing case (it's a bit difficult to explain, but I'll try): Previously, you could have a thread where a comment has a few replies ("A", "B", "C"), and the first one has a string of single replies ("A2", "A3", "A4"). If the flattening applied, you would have all 6 comments displayed on the same level, in the order of A, A2, A3, A4, B, C. It was very difficult to tell where the "A subtree" ended and it went back to siblings of A—you had to look for where comments stopped having the "(Reply to above comment)" note on them.
Some people suggested that we use a more obvious indicator of the flattened threads (which might still be a good idea), but this case should now be avoided entirely, which should reduce a lot of the potential confusion when threads are flattened. This also means that the flattening will apply in fewer cases overall, but it should still work for the most common and impactful case of a long string of single replies going back and forth.
As mentioned in the original announcement, one of the nice parts of managing to do the flattening entirely in CSS means that it could easily start at higher thresholds on larger screens, so that threads aren't flattened as early on desktop/laptop-size screens as they are on mobile. I've applied this now, and it should now be very rare to see a flattened thread if you're using the site on a PC.
If you want to see this in action, you can go to a thread where flattening would apply (the ~tildes.official thread about "source info" is still a good one), and try resizing your browser window to see how the flattening kicks in and adjusts at different sizes. If you're using Firefox, an easy way to try this out is to press Ctrl-Shift-M to go into responsive design mode, and you can easily resize the viewport or set it to specific sizes.
Other than these changes to the flattening behavior, I've also merged in another open-source contribution that adds alternate sorting methods on the user page. These only appear when you're on the Topics or Comments listings (not the default "mixed" page), and allow you to sort by the other methods available, such as "most votes". Note that since those Topics/Comments pages are only available to logged-in users, viewers without a Tildes account won't be able to use these alternate sortings. Thanks for the work on this, JediBurrell (whose Tildes username I don't know either)!
Let me know what you think of these changes and if you notice any issues with either of them.