From the guidelines:

> When disagreeing, please reply to the argument instead of calling names

Though this might also equally apply:

> Be civil. Don't say things you wouldn't say in a face-to-face conversation. Avoid gratuitous negativity.

>oh wait you're a fool and a coward.

I shouldn't feed the trolls, but the irony of calling someone a coward while posting from a throwaway account is too funny.

And yet ... such labels are often accurate.

I'm aware the HN guidelines are geared at productive discussion, though there are times I strongly suspect that's not possible.