TL;DR: Fall damage is INCREASED if you crouched since your last jump. Jump before dropping from top screen to avoid taking damage.

My friends and I just discovered an insane bug that's been in the game for a long time (I don't think it's been discovered before):

You can see this on Icebox top screen, if you crouch (you need to wait for the animation to complete) and drop from top screen you will take damage. If you jump and never crouch again you won't take damage.

To get to top screen most people crouch, and that's why you take damage if you drop*, if you instead get to top screen without crouching, or if you jump after reaching the top, you can drop full running without taking damage.

*: You used to be able to walk off the edge without taking damage even after crouching, it appears like this doesn't work anymore

Video demonstration: https://youtu.be/PMtn99S2Zow

Video description:

1. First jump: Crouch to get to top screen, run off => Damage
2. Second jump: Crouch to get to top screen, jump in-place, run off => No Damage
3. Third jump: Crouch to get to top screen (irrelevant), jump in-place, crouch, run off => Damage
4. Fourth jump: No crouch to get to top screen, run off => No damage