It is now possible to enable/disable dark mode separately for the interface and the map background.
Be log → Click on your profile icon → My Preferences → Edit Preferences → Change the “Preferred Website Color Scheme” and “Preferred Map Color Scheme” to “Auto”, “Light” or “Dark”.
Thanks! For clarity, I’d suggest renaming “Preferred Map Color Scheme” to “Preferred Map Brightness”.
Following the discussions on Github, I believe the reason for this is that in the future there will be proper color schemes in dark mode, at least for some of the cartography styles.
Is it better now since I was allowed to turn the dimming off?
And that got closed instead.
It is, yes, and thank you. The only thing I find a little odd, is that you need to be logged in to be able to do this.
Since yesterday (?) I don’t need to be logged in anymore to see the undimmed tiles in dark mode. 
