Have there been mass multiplayer chat based rpgs?

I was playing around with this idea of a city where every region is a chat in a discord server and everyone has their own character who is playing in the city and they can be anything they want. obviously it would run on a system and have dice and stuff. And then when two or a group of players want a private rp they could open a ticket which only them and mods could see. of course there would be mods that would enforce the rules and stuff. it probably already exists. and if it does point me that way pls.