Of course my problem is not that I had to write CSS. Not at all!
But some other developer/eshop owner might need this. And styling this extra table cell requires some extra custom CSS.
And last, the Customer details are also not visible in the editor, while it shows up in the live thank you page after a completed order!
Is this some kind of bug, or some sort of normal behaviour?
I just deactivated all plugins, and I had the same result as you (as it should be). Then I activated them one by one, until I got all of them enabled just like before.
And from that point it just remained correct, as if nothing happened in the first place!
Do you have any idea what could be causing this weird behaviour?