Let’s say that some users in one topic have started posting irelevant stuff to the current discussion or you think it’s about high time for a break. What you can do is call a Time Out by closing the topic for some hours. That’s what system does automatically when there have been many posts flagged in one single topic in a very short period of time. Messages play a crucial role too, I don’t disagree with that. But keep in mind, that when the user is angry, they will get angrier if they receive a warning message from the admin team. Furthermore, a member of the staff team can step up and calm things down. They can also moderate the topic by deleting posts, which will cause users to argue more.
You can also ban everyone! Nah, I am kidding, haha.