What I expected to happen was...:
That mobs, such as creepers take damage from jumping on the stalagmites, or most specifically their top/peaks.
What actually happened was...:
The mobs avoid any of the damage that the player can get, even though they jumped the same way on top of the pointed dripstone; only take damage while falling from a high place directly on them.
Steps to Reproduce:
1. Take any terrestrial mob spawn egg
2. Spawn the mob on the stalagmites(rows of them with walls on sides)
3. Look for when it tries to jump to get around
Walking or jumping up on a stalagmite is not supposed to cause damage. Standing on a stalagmite and jumping up and down should hurt, plus jumping down onto a stalagmite from a higher position. But in general, both mobs and players should be able to walk around on top of stalagmites without getting hurt.