i_feel_safe() ignores monsters that it thinks cannot attack you, but there are two cases where it is often wrong about that:
1. It believes that monsters across deep water/lava are safe if they cannot cross the water or lava and do not have a ranged attack. However, this fails to account for polearm reaching, which monsters can use to attack across water/lava. This is most noticeable in bailey_polearm_1 where every 'o' press will cause you to get hit.
2. It believes that monsters cannot get through plants or bushes. However, monsters will attack plants and bushes and therefore can get through them. This is most noticeable in Lair where autoexplore will occasionally fail to stop for a hydra or 30 killer bees because there were some plants in the way.