Essentially the mobile header is taller than the actual content and looks off.
It should look like this:
CSS property that needs to be adjusted:
This is the change that actually introduced the “bug”
https://github.com/discourse/discourse/commit/911f941da543f7b44ddf457099aa97cb31947076
The height should be adjusted, or better yet we should find a better way to style it that doesn’t involve hard coded pixel based heights.