The communication view shows all comments made in the whole board. So the communication does not only refer to one task, but to the whole board.
1. Select the communication view in the board settings
2. Here you can directly create a new comment and assign it to the desired task
3. Alternatively, you can create a comment without assigning it to a specific task
4. Settings about what to show in this view can be made using the gear in the board menu bar