These types of conversations are generated from tasks either automatically (i.e. a new task has been created) or manually from a particular task right panel. Each conversation is composed of Comments. Again, those comments can be generated by the system automatically (i.e. task has been put on hold) or by a particular participant. They cannot be started from Communications view since they must be related to a particular task and project.
A user can also start a conversation at any time with whoever they choose. Conversations can be started from Communications view or from the +NEW button from any screen.