I actually use HN frequently as a tool to concentrate better during work. I often juggle quite different tasks that I have to solve at work. To flush my mind and go from one finished thing to some completely unrelated next task, I jump to HN, read some things, then jump back to what I'm supposed to do. The important part is to have things actionable and with a definition of when they are 'done', so that you can close them and do the next task.
In 30 seconds, we can go from fully intending to do something that we should do to better ourselves to reading HN submissions and commenting on them.