I’d still suggest investigating if Discord has or could be modified to include sub-threads for tangential discussions, that trail off from a post.
Full discussion trees, like you get in reddit, disqus, etc. are horrible and useless for any discussion between more than 2 people. But Slack’s “linear with subthreading” system does work well. It allows the main flowline to stay on-topic, while allowing people to clarify, argue minor points, etc. in a tributary, keeping the mainline free.