Recent discussions have brought up an old issue on how Flarum handles (performance-wise) large discussions or so-called "endless threads" with 20k+ posts.
Fundamentally, I think the design of Flarum design on discussions does encourage such large discussions. Many use cases exist for such long discussions (discussions about orders, games, RPG, etc.). I think it should be explored if there are tweaks to be made to increase performance on such long discussions without sacrificing the core principles of Flarum.
Other big community forum software providers have opted to go the route of enabling chat features. I do not think this is the way to go as there are plentiful options for chats and this is not a unique feature of discussion forums. They exist for a certain case - and people who join a forum want to have lengthy discussions in forum style.
I do think this needs further discussion especially if more information is available.