Topic: Offense Perk "Head Hunter"

“Gain +10% chance to hit the head for critical damage each time you hit the body. Bonus is reset upon hitting the head”

Not sure if it’s working like intended so please allow me to ask some questions.

1) does this effect stack? (or only up to +10%?)
2) does it only work against the enemy which you have hit his body once?
3) the reason I’m asking the questions above is because I don’t see any increase in “chance to hit head” stat nor do I see any tooltip/description indicating whether the effect has triggered.

Thanks in advance.