Comment by c22

I think background color and text color options with inverted voting arrows (as suggested elsewhere in this thread[0]) would be enough for most people.

What.cd used to let you put a url in your settings that was injected as the stylesheet while you were logged in. This approach would let people publish and share themes--though shared themes could be a (pretty visible) security concern.

I remember also running into issues trying to use non-https-served stylesheets since the site was https and browsers balked.

[0] https://news.ycombinator.com/item?id=23199725