Thank you for your answer. the person received fake trust is my friend. and the person who give fake trust was active last on 2015 year..
There would be no issue as the person who posted negative feedback is not on default trust list (that means profile won't appear red). I don't think mods will interfere in this matter unless it is and critical issue as the trust system is created in such a way that the only poster can alter or remove feedback. You can ask for help, but I don't see much chances.