You're basically forced to accept the flat discussion view, which is completely unworkable to review a long and branchy discussion.
There are two more fundamental problems with long and branchy discussions: they're long, and they're branchy ;-)
But they are also unavoidable in any realistic setting. The idea of Discourse seems to discourage such discussions entirely. But that only works when the problems are simple and well-defined enough.
If your idea of what "works" is the typical long-and-branchy contentious thread on Python-Ideas, we have incompatible views of what "works" means ;-) I don't care if something like that is displayed in a 30-dimensional graph structure cross-linked by date, author, reply-to, keywords, and semantic relevance, there's simply no clear sense _to_ be made of such stuff.
The "Python Governance Electoral System" thread is as long and branchy as a discussion has gotten there, but is more :"civilized" and on-topic than most mailing list threads of similar complexity I've seen in recent years. It worked better than I expected it would - although I was an active participant.
Making it very easy to multi-quote, with live clickable links to both view and jump to the original messages, is really very nice. _Lots_ of things are nicer than mailing lists. And other things aren't. So it goes.