Having the slow fall effect negates damage taken from stalagmites.
What I expected to happen was...:
Take damage from stalagmites as normal
What actually happened was...:
Absolutely nothing.
Steps to Reproduce:
1. Place Pointed Dripstone on the ground
2. Give slow fall effect
3. Jump on the stalagmite.
This is because stalagmite damage technically counts as fall damage, which slow falling negates.