I use a Daylight computer, and dark themes always look terrible on it. I'm obviously in the wildly small minority for this case, but I appreciate at least having the option for a light theme for things.
I don't use e-ink, but I have astigmatism and dark themes are difficult for me to read, especially really dark high contrast themes (white text on black background), so I pretty much use light themes almost exclusively, even at night (I just turn my brightness down).
So I agree, default to whatever you want but definitely keep an option for a light theme available for those few of us that prefer it.
FWIW I don't prefer white themes either, I like something like solarized light or gruvbox light
Please don't use HN primarily for promotion. It's ok to post your own stuff part of the time, but the primary use of the site should be for curiosity.[1]