The lines remain the same in terms of breaks and positioning. See:
Entering characters does update line breaks. It's when you enter a series of returns, or delete a series of empty lines that the breaks don't update. I expect there's some optimization that assumes a square box. Perhaps this optimization is turned off in the presence of floats and this could be extended to the presence of shapes?
It's been fixed in the meantime, since it doesn't occurs anymore. Closing bug as worksforme.