(More examples are here and I think the styling bug isn't affecting this page: https://docs.mycoder.ai/docs/examples/ I will look into the bug you ran into.)
They're likely running the Dark Reader extension and turned it off for the site, but didn't refresh the page. The extension doesn't always fully reset when you disable it for a specific site. Reloading the page with the extension turned off fixes the issue, so it is not your site.