One thing the mods can maybe play with in this area is “Slow Mode”, designed for contentious topics. When activated, “Slow Mode” limits the number of sequential replies any given poster can make.
To activate it, mods can use the wrench action at the topic level:
Then decide what the time limit is, and the duration of Slow Mode 
→
It’s a tool in the toolkit, and we think it works very well in some circumstances.
You can also do a timed closure, so the topic is closed to all posts for a certain number of hours. That’s available via the same staff wrench menu pictured above, look for Set Topic Timer then select Close Temporarily.
Sometimes it’s good to slow down. Sometimes it’s good to have a time out for a bit. All tools in the moderator toolkits.
(these pictures were taken on my own personal Discourse instance where I am staff; I am not a staff member here, just a person knowledgable about the open-source Discourse project.)