Shameless self-plug: I built Refined Hacker News[0], a browser extension, that allows one to set custom CSS and has a default preset for dark-mode :).
I have one minor issue though: the top bar (with new threads past etc.) is white with the text almost white too. Makes it unreadable. I'm not sure if this is somehow my fault or if it comes from the addon: https://i.imgur.com/DPEn3b6.jpeg
I have dark mode on.
This is an interesting issue. What color is your "topbar" configured to? You can check it under your profile settings: https://news.ycombinator.com/user?id=Krasnol. It could be that the topcolor that you've set is a dark color, and the CSS inversion makes it light, thus conflicting with the text color.
If this is still a problem, please do open an issue on the GitHub repository, I'll happily look into it :)
Thanks :)