Naven
Glossary
Group chat
A conversation with more than two people in it.
The mechanics are simple and the social design is not. A group that anybody can add anybody to becomes noisy; one only the creator can change becomes stale when they leave. Notification defaults matter more than in a direct conversation, because the volume is higher and most of it is not addressed to you.
The common failure is a group that nobody wants to leave for social reasons and nobody wants to read.
Where Naven stands
Naven groups are made by naming them and picking people from conversations you already have, or by email address. No phone numbers are exchanged in either direction.