the existence or non-existence of a trademark registration filed with the USPTO doesn't necessarily mean that the name is trademarked or not. registration helps when you're suing, but trademark rights can attach without registration.
It also occurred to me that hackernews.in is clearly a website aimed at Indians, so I don't know to what extent US law applies.
Anyway, it seems that the name is going to be changed, so this whole trademark point becomes moot. http://hackernews.in/item?id=375