As of right now, you need to pay $5 to access the dark theme. I believe this is stupid as it is clearly more appealing and the first impression is very important. Not much more to say.
I just feel like you shouldn't need to pay to unlock the sites most appealing form. And I also wouldn't worry about all the other forums.
Dark theme access is one of the main reasons why people buy Diamond in the first play. Remove that, and you cut a big income source.
There's only a small selection of perks you can give for people who purchase account upgrades, and a dark theme is a popular choice. I don't see why we should make it free to all users, if people are willing to pay for it, which in return funds the site.