Only Law Can Prevent Extinction — LessWrong

Comment by Caleb Biddulph - I think it's very clearly wrong according to standard English grammar rules, but I also think that Eliezer knows that and is using the comma to simulate a conversational speaking cadence. In this case, it's a pause for effect that emphasizes a sense of absurdity that this has to be said, in a way that "The utter extermination of humanity would be bad!" doesn't.

It would be more grammatical to use an ellipsis ("The utter extermination of humanity... would be bad!") but implies a slightly longer pause, which is probably less accurate to how Eliezer would say this out loud.

This kind of comma usage would be inappropriate for, say, a newspaper article, but I think it's defensible for an informal persuasive essay.