When Kovu was exiled, do you think Rafki should have went to Simba and have told that Mufasa wanted Kovu to be with Kiara?. Or perhaps Mufasa himself should have shown up to stop Simba and make him change his mind?.

Honestly I don't know how this whole thing with mufasa's spirit is working.. the fact that he does give signs to rafiki but not to simba doesn't make any sense.. Simba had nala though :P I don't think that he would listen to anyone, not even rafiki after kovu's exile as he was certain that kovu was still an enemy

He probably would but Simba would probably not believe him and ask questions that Rafki is unable to answer, so I think he had in mind to let them figure it out but since the ambush happened it about crumbled the idea but what kept it alive is Kiara was already in love with him. And even if Rafki did at the time with the exile the call would of already been done and he'll have no power to stop it probably. :P