Yeah I discovered this bug in Tyadran's Playable Kane Mod. Hans cannot be promoted in that mod because he's in Jogurt's slot. Jogurt was replaced with Kane as a playable character in that mod. Normally this would not be a problem since Jogurt has never been promotable from the start but the problem comes from the fact that if someone else is put in Jogurt's slot they will not be promotable anymore. It will appear as though the friar is promoting them but once you check you will see that nothing has changed just like with Jogurt. And this would be a great new feature to add to the editor for the reason Erikin said.
I really do not understand why anybody gives a crap about Jogurt. He's a dumb and useless character. And it's just an outright INSULT that he got to be the face of the franchise. I'm glad Fire Emblem at least got an appropriate mascot.