> I say this as a (begrudging) discord user : I don't know what they (Discord) did right to get communities to lock up all of their community and data into such a hard-to-index walled garden.

Completely anecdotal, but IMHO their app just works and it works well. For instance I used to play an MMO using discord and we had ~72 people in voice chat at any given time and it was flawless (some of our members were 80+ years old, the game I played is 25 years old). Meanwhile at work (I work in IT) it's not uncommon to spend 5 minutes just getting a meeting started, figuring out why the mic isn't working, trying to get someone to mute who isn't, etc.