I don't know whether these stories are pulled by HN moderators or flagged by lots of users but there is more than one motive for pulling/flagging stories. One

I don't know whether these stories are pulled by HN moderators or flagged by lots of users but there is more than one motive for pulling/flagging stories. One motive might be to avoid unproductive discussions - many of the comment threads on the Greenland story (which I voted up) were angry and very polarised.