I don't know quite what happened, I was getting frustrated, trying to somehow escape the backticks inside the code formatting. I clicked the edit button too many times, and then the above happened. Perhaps I clicked it to fast, I don't know, but I then got lots of boxes.
Based on a test case below, the problem is simply caused by pressing edit while you still have an edit box open. They all go away when you press cancel anywhere once. This makes it much easier to reproduce, and, while not very important, perhaps still something to be fixed.
Note on the pattern:
When you click the first time, you get one box, as normal. When you click again, you get one extra empty box at the top, and another normal box above that. At each click, one empty box is added per existing normal boxes, plus one normal box. What is going on?