I can't speak for HN's motivations, but my view as a web developer has always been that, in general, target="_blank" is bad. My reasoning is twofold: 1) It's unnecessary. Opening a link in a new tab is easy for the user to do with a keyboard modifier, if that's what they want. 2) Worse, when you use target="_blank" you force that behavior on every user. There's no keyboard modifier to negate that behavior and keep the link in the same window.