The crazy thing is that people are suggesting things that should simply be added on as a function of the site. It's 2019, Dark mode is here to stay, why not just add it natively instead of having to install yet another plug-in/add-in/extension?
Because I disagree; user preferences should be a function of the client software rather than a function of the site. (This is especially true when the web page does not have its own CSS, or if it is a plain text file; then the user preferences on the client are used to decide the fonts, colours, etc. The web site shouldn't care about this.)
