Please don't use names like “liar” or obsess over upvotes and downvotes. Even if the other commenter instigates the poor behavior, we can't have this kind of escalation or the place will go up in flames. It makes it harder for us to act against the instigator when you do this. Please just flag bad comments and email us (hn@ycombinator.com) in egregious cases.
https://news.ycombinator.com/newsguidelines.html