Depends on the MUD type. I used to play, admin, and sysadmin on AVATAR MUD, and the sheer text scroll of a large group in combat just wouldn't translate to WhatsApp. A lot of the players used TinyFugue with complexish state management in the scripting to highlight things going on in the combat output.

Now, Hitchhikers Guide To The Galaxy as a text adventure game over WA could be interesting for some people.