So much this. Many (most?) oldstyle forums suffered from a pretty strict no-duplicate rule even in “free talk” sections. This led to few oldtime gatekeepers dominating these places, new post anxiety and general stagnation, because new users had no way to learn occasionally or talk about things. When I started to visit HN, it was so relieving to see that well-separated duplicates don’t get moderated away or even discouraged. It simply means that you can eventually learn what you don’t know yet or missed for some reason, can participate/discuss it from a today’s point of view and renew your understanding.

Repetition may be seen as a visitor’s expense, but appreciating it creates a huge net profit over time, cause it helps a community to stay fit and alive.