I tried MUD a few times as a teenager, but for some reason I didn't like it. I prefered playing RPG on a long dead phpBB forum (LdC), and to this day I remember the very simple mechanic (for both players and gamemaster): an asterisk for character speech, and (#) for everything else.

A single post might look like this:

    # By hearing those absurdities, memories rush to the mind
    of Vicent Panclast — memories he'd like to avoid. He gets
    physically agitated and raises his pistol high in the air.
    * They shall not pass! We must do anything we can to stop
    these mf nazis!!

I wonder what something like that could look like with the right use of AI, today. I'd like to think kids are exploring this kind of thing nowadays - I hope they are, because it's a ton of fun (even without AI, kids).