Trololo, super strange: I posted this and immediately got to your post. Assumed it’s some nifty mechanism to avoid double posting since we published the same URLs but you were a few minutes earlier than me. But apparently you could make your post despite the previous one you kindly linked to. Did we find a bug in HN??
The previous one was a couple days ago, they obviously have a time threshold (ie a feature, not a bug) but the rapid drop of this off the front page probably indicates a more nuanced approach.