Product: PowerShell Universal
Version: 4.0.1
Hi Adam,
it looks like that the UDCodeEditor show up with light theme on the first time.
First Select:
Change Theme to light and back to dark:
Change Selection:
and now it is light again 
and by the way:
Is it intended that the UDCodeEditor only adjusts to the size of the window when the page is opened or when F5 is pressed?
These are both bugs and I’ve opened issues for them.