Use server nick instead of Discord's one

[LuisMayo]

Currently we try to do it but it doesn't work

[GrJT]

Maybe you should change this line in file 'message.py' at line 39
return Comment(user_id=self.user.id, user_name=self.user.name, text_content=self.text, evidence_path=self.evidence)
self.user.name -> self.user.display_name