alt Hacker NewsThere's also really nothing to a community beyond its mods, its users, and maybe some bots. Reddit creates a record of EVERYTHING and in many ways those years of discussion are the sub more than the current users or mods alone. Discord is nothing like that, if you could get everyone on the same page a Discord clone would work just as well, and relatively seamlessly.
tl;dr Discord has a moat, but it's not very wide or deep.
That's not true. Plenty of Discord communities have dozens of channels with long-running post histories, pictures, FAQ content, beginner guides; server roles and titles, permissions, custom emoji, stickers, etc.
Migrating all of that stuff to a new service (which may not even support it all) would be a huge pain.