Steps to reproduce: In an empty document, press 'x'; set it to be a heading; press Home, Enter, Enter, Backspace.
Expected behaviour: The cursor appears at the start of the second paragraph, just before the 'x'.
Observed behaviour: The cursor appears appears inside the first (empty) paragraph (just before the chimera).
Changeset 9367efb90ff689f840da33fdcb95e514b1322cb9 was when this broke.