Thanks! It's always nice when fixing a visual bug to include a screenshot

It works, but... why is there a border there in the first place? I'm always uncomfortable with bugfixes I don't understand.
And why separating instead of sharing borders would prevent it from being shown?

The point of the transparent border is to allow the green and red highlights on the left when hovering:

You can get alignment issues in tables with border-collapse where he green border takes up more space than the rest of the tr so it tries to align it by adding a border around the next element.

But with separate borders this compensation is not needed