I've taken about 5 hours to cobble together a usable dark theme, I might make a thread for suggestions on it and stuff. The link is here below if you want to try it out, you install it using Stylish.
https://userstyles.org/styles/153233/mlpf-dark-theme
The known bug right now is that the blogs are unsupported. There are so many differences that I will need to take a closer look and make a separate stylesheet for that. I also forgot to apply it to profiles, fixing now.
It now supports profiles. My bad on that one, I'd gone through every other link I could think of, and I've missed a couple. If something's broken, make sure you revisit the page and download the update.