Hi Paul,
The dark scheme is basically fine as it is.
If we are looking for further improvements: on the normal (light) scheme, the bold font for highlighting unread topics is very distinct. Far less so in the dark theme. It does work, but just isn't quite as conspicuous. I wonder if there is a way to make it more noticeable. Maybe a heavier font?
Separately, in the same way as very light beige or off-white background is easier on the eye than stark white for light schemes, I wonder if a very dark grey (off-black?) would do the same for dark themes.
Those questions don't mean that anything is wrong with the dark theme as it is.