From the medieval days when a person took a needle and tried to find a witch's mark ( a area of skin that wouldn't bleed) and prove a person was a witch. The pricker was paid for their work and would prick a person hundreds of times to find a witch's mark. modern context would be a person who tries to find anything wrong with someone so they can deliver them to somebody and receive a profit.
Mark is the office nark, a real pricker. Anything you say to him goes to the boss and is made to sound as bad as possible. He has out lasted everyone here. Mark also asks the people the boss doesn't like a lot of personal questions.
"Pro" means "for" as in for something.
"Vert" means to turn.
"provert" in favor of truning.
Thus a provert is a person for gain or pleasure, may knowingly causes the unwanted turning of a victim down a certain path of events which leads to perversity. A creator of perverts.
The adult provert (who was mad at the store)dared a small kid to toss a rock through the store window. Then from a distance, watched the kid do it and get punished for it .
The proverted interrogator asked the innocent suspect if the suspect has ever stopped stealing from his employer (logical fallacy called a compound question). Knowing that either a yes or no answer will make the suspect look guilty to his employer but make the interrogator look good.