I believe I had no enemies in LoS during those turns. Even DCSS warns "You are lethally poisoned" in similar situations, here Demon might give "You are going to die next turn, are you sure you want to move?"
I don't like that I need to pay attention to 3 places - main view, HP bar and message window. For example, it could be a flying tooltip "-11 HP" when my main character loses 11 HP from an attack or ignite.