I defined this distinction to an older relative about a year ago (right after I apologized for "geeking" all over her shiny new coffee maker, which I had taken apart and put back together). To illustrate, I used music. A music nerd knows which years qualify as classical or baroque and which composers wrote what. A music geek tunes their own piano.
I don't think that a place called "Hacker" News is going to be overly concerned with popularly accepted definitions. Otherwise we'd all be complaining about the lack of 2600 articles and Kevin Mitnick blog entries.