Kerry is correct. MIR should be filed with Collaboration as the main issue, but make sure to include that previous merges have been rejected with the reason and make sure that all wikitree IDs are included. MIR should be filed for the person that is rejecting the merges by following the Problem with Members link. That person will not know who filed it, it is strictly confidential. Only the people reading the MIR and the person that is assigned as the Mentor will know who filed it, so they can contact you for further information, but it is always best to try to include as much as possible.