I hate the formatting of most forums. Reddit and Lemmy’s comment nesting is excellent.
The funny thing about this is that it’s just plain old threading, which has been around since the 1980s or earlier, with the slight variation of showing message contents directly in the thread tree instead of beside it (thanks to today’s high-res displays).
Usenet readers did threading. Email apps could do it if the developers wanted to; the required information is there. I’ll bet there’s forum software that can do it if an admin enables it.
For some reason, most corporations seem to have decided that classic message threading has no place in their interfaces. They resort to piling things into stacks or serializing them into seemingly endless scrolls. It fails to represent the structure of group discussions, and sadly, has been going on for so long that many people might not have ever seen the better alternative outside of reddit.