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Final note: I just hoped such behavior can be punished if i can provide all the needed information.
The forum will not penalize such behavior, the forum will not interfere in a user's business affairs. Even if you are looking for a defense here, the consequence is simply the tagging of members which is sometimes subjective.
The user action is already closed to extortion since he start posting negative comments and false accusation about the project after he didnt get the payment that he ask for a
volunteer work. This is merely a subjective case because he made the attack on the project after the OP denied the payment for the work that he volunteered without any payment notification for the project.
A neutral feedback from @Bitcoingirl.club and his reason is right. He might done this on many project before.