Another person trying to make this a "Hacker News vs. Reddit" thing, which still doesn't appeal to the reason sectors of my brain. Definitely not a ripoff; Mashable's clearly grasping at straws again.
Yeah, if posting comments and replying to comments is a design rip-off, then every forum in the world is also a rip-off. Hacker News looks nothing like Reddit, and the internet can support more than one discussion site (obviously).