I think it looks too plain.
The reason why Sanctuary v1.0 is better, IMO, is because the "message-cell" div is a different color than the background, whereas in night mode, it's the same color.
If you make the background a different color, maybe matching the color of the "fr-wrapper" (this text box I'm using), I think that would work. That's how it is in v1.
You'd also want some contrast between that and the other colors. Basically, don't let the same color border itself.
Basically, just make it Sanctuary v1