Isn't this more of an argument for a better UI around managing groups?
Seems like the author wants the chat UI to be used to created or edit groups.
I think that each of these chats or groups should be looked upon as new separate circle or list of people. Like a lot of friend lists, which overlap, cross etc., but without the updating hassle.
I have always been lazy to update those lists. Now I see the logic behind that. :)