>>12724949But in that instance, yes. Shut up is a command and without the comma, you're not commanding the second person stupid autist to shut up, you're telling the stupid autist to shut up some other second person stupid autist.
It's like "It's time to eat, grandma" compared to "It's time to eat grandma". The former is a nice gesture while the latter is sort of cannibalism and probably doesn't taste very good.
