In 2000s "Neumorphism" would have been a name of one WinAmp skin. In 2020 I guess a single style warranted a whole trend.
This is in the site guidelines: https://news.ycombinator.com/newsguidelines.html.
You needn't use your real name, of course, but for HN to be a community, users need some identity for other users to relate to. Otherwise we may as well have no usernames and no community, and that would be a different kind of forum. https://hn.algolia.com/?sort=byDate&dateRange=all&type=comme...
Creativity in this domain is undervalued.
It's a design language that doesn't get one into a PR trouble, I get why it exists.