Long threads are a difficult problem for any online conversation. This site uses Discourse, which keeps track of which posts are replies to others, but presents topics in a flat model rather than with nested threads.
I think in general — here or on mailing lists! — any online thread gets pretty hard to follow once there are more than a couple dozen replies. Discourse has a site tool which can help us have big conversations while keeping each topic… topical. It’s called “linked replies”, and it works like this.
When you start a reply, you get a form like this:
Notice the little arrow in the top left. Click on that, and you’ll see that it’s not just decorative: there are actually a couple of options!
Choose “ Reply as linked topic”, and: tada! You’re now creating a new, linked topic instead of adding a reply directly in the current one.
Write a new title describing the new issue, add tags and change the category if appropriate, and post as normal. This works when quoting something from another post, too.
When you do this, Discourse will also automatically create a link “mini-post” in the original topic, so that other people can also easily find your follow-up.
If you reply in a topic and then later realize a new one would be better, you can flag your own post for moderator attention. Moderators can split threads after the fact. And of course, feel free to flag when you notice a large tangent growing in any thread.
This is helpful for future visitors who will be able to catch up on the main thread of topic more quickly, while still allowing deep dives into particular areas — or complete tangents inspired by a conversation.