alt Hacker NewsIt’s a common HN practice. I’ve done it once or twice. Mods will do it often, especially with highly active topics. I imagine it started as a method to avoid duplicate posting thereby consolidating conversation and, also, so that karma attribution goes to whoever the original poster was.
I imagine automation would be difficult because the same topics come from different sources and occasionally there is additional/novel information in similarly titled postings.
Also important to note there is a time eventually that something is no longer a dupe, and people will still add previous discussions about it (often dang himself), because the previous conversations about the topic may be of interest. But unless some earth shattering research just came out in the last three days showing that lead is good for us, actually, it hasn’t been long enough for that to apply here.