Given how pedantic and cargo-culty the HN community can be about even the tiniest detail of the layout here, it doesn't surprise me that the mods don't make it a priority. The arguments about implementation details and edge cases would be ceaseless, and people would clutch their pearls about HN "turning into Reddit."
Also dark mode seems way too modern a feature for a forum whose entire aesthetic is frozen in the 1990s. Dark mode doesn't directly improve the signal to noise ratio or quality of conversation.
Maybe the best solution is to just let everyone use whatever plugins or browser scripts they want to and leave HN as it is.
In my earliest days of using the Web, I used lynx. The text was light grey, and the background was black, for that was what my system defaulted to and I liked it well-enough.
Later, I used Netscape. Some of the more prominent settings[1] were for default colors: For text, links, visited links, and background. I very quickly made it white on black (but kept the blue/purple links unchanged).
But that was just me attempting to stick to my own familiarities.
For most others, the default background in those days was also not white; it was instead grey (#c0c0c0, [2], [3]).
Backgrounds defaulted to grey with Netscape all the way to the end, with Netscape Communicator 4.8 still defaulting to grey [4] at its 2002 release. Mosaic was also consistently grey [except for on the Macintosh], and so was IBM's WebExplorer (the forgotten independently-developed web browser that shipped with their forgotten desktop operating system).
Even Internet Explorer remained grey by default until the release of version 4, in the last half of 1997. [5]
But you're right, of course: There's no need for dark (or grey) mode here on HN. It's a simple-enough affair for a person of sufficient wit to change it to whatever they want, in-browser, here in 2025.
Like I keep pointing out time and time again, when I read HN through an RSS reader the embedded browser cannot run extensions and I get a white flash in the middle of the night when I click over.
Also dark mode seems way too modern a feature for a forum whose entire aesthetic is frozen in the 1990s. Dark mode doesn't directly improve the signal to noise ratio or quality of conversation.
Maybe the best solution is to just let everyone use whatever plugins or browser scripts they want to and leave HN as it is.