The application title bar (the one with the close, maximize, and minimize buttons) turns dark when dark mode is activated.
The application title bar stays white. It’s a minor thing, but having that disjunction clashes with the super sleek UI of the app.
Not sure but I think this is an OS level thing. My not so smart work around right now is to hit F11 and hence make obsidian full screen. That way I don’t have to deal with seeing the eye blinding title bar while in dark mode 
It should be possible to change the titlebar/frame with some simple css/python scripts (similar to what the Notion community did to it with Notion Enhancer).
Despite this being a relatively small issue it’s nontheless something annoying that should by all means be taken into consideration.
I’m experiencing the opposite problem: I use light mode but the window title is dark.
If you check the above option, the title bar of Notion will change to your accent color when in focus. However, once the window loses focus, it goes back to bright white as the accent color is no longer applied.
Either way, Notion is not following the system colors of Windows:
