dang is a mod—as far as I'm aware, they are the mod. When a previously-covered story crops up again, they typically add a comment like this with links to previous discussions, so you can easily see what was said before.

oneeyedpigeon already explained it, but allow me to follow up with more information:*

You can see a zillion examples here: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...

The purpose is to satisfy extra-curious readers (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...) who might want to read previous discussions of the same story.

No criticism is intended! I add this because sometimes people think there's an implied "why did you repost this, it's already been discussed" - but not at all: reposts on HN are fine after about a year or so: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...

* than you could possibly want, but oh well