It’s sort of like metadata, your right about less “in Java/C/etc” but there are other languages that are more vocal about indicating this, Python comes to mind, Go is a semi-frequent user of the “written in” addendum. I like rust and I like seeing the growth of the ecosystem and discovering new libraries like this. To me having this is a big help. For a language I don’t like like Perl or Go, its also nice to know I can ignore it, or alternatively check it out to see if anyone suggested similar libraries in other languages, something which happens often enough I got into the habit of quickly skimming such threads for links.

There’s value in the metadata of “written in $X” allowing you to know what to expect. If HN had tags or something like that we could filter it instead but it doesn’t and so we’re all just experimenting with alternative labeling schemes.