One of the only differences between new Reddit and Discord is that Reddit has the courtesy of a public index.
I don't know much about Discord (my only experience being some years ago when I joined for an open source project and left soon after I noticed how incredibly use hostile it is) but I do know that if you create a single account it is trivial to join any "server" (which, despite the marketing is just a chatroom hosted on their servers).
> I do know that if you create a single account it is trivial to join any "server"
Only if it's public. There are many private Discord servers.
The way they do it is that the default set of permissions is basically none, but then there's a server role which actually gives you permissions to see the channels and post in them. So, anyone can join the server, but only people who have been granted this role (e.g. by admin) can do anything on it, or even see others.
We're gonna enter a new age/type of "lost media" as Discord remains popular year over year. It's a complete black hole unless you're manually backing things up. No possible Wayback Machine.