From what i tested using
displayall KFSeasonalEventStats_Spring2021 bHitTakenThisWave
What counts as if you've "taken" damage, might be more. If one feel boring try it out.
- Grenades that don't normally do self damage (Flashbang, Molotov or M203 incendiary + 100% fire resistance)
- Self healing from Hemoclobber's heavy attack
- Gravity Impoder projectiles (despite not doing any damage to player)
- SWAT and Survivalist's armor bonuses that allow it to absorb 100% damage do not help, you still "take" damage
- Walking over your Husk Cannon's ground fire or M203 Incendiary's ground fire (other GFs do not "damage" you)
- Having another player landed on top of you
- Exploding Seal Squal projectile under your feet while having Destroyer of Worlds in ZED Time (and probably Mad Bomber too)