Zombie H1 Style

1. Edit a post
2. Go on new line (empty)
3. Header → H1
4. Type "One two" + Newline
5. Type "Three"
6. Delete "Three"

As a result, the caret will be in the third line. Notice that the H1 font size will be restored. Typing new text will result in H1 style.

Props to @folletto and @iamthomasbishop for spotting this one!