What a wonderfully-told story. Your Ivo is so very likeable, both the young and the old version of him.
Ah, but we have no such chance, my dear, Ivo thought as he shook her hand, human nature being what it is. And he's right, of course.
Last and least, he would talk for the sheer kick of it He's so completely honest: that would be one of the reasons, perhaps the main one, to speak.
And the glimpses we get of Snape and McGonagall are completely IC, yet revealing as well. The snark, the banter, the House rivalry (and pardon me, Professor Snape, but to me "Even your sarcasm reveals you as a Gryffindor, Minerva. Always that lamentable lack of subtlety. . ." is considerably less original than Minerva's comments. 1-0 for Gryffindor, I'd say ...) But in those few glimpses, you also show so much love and tenderness between them.
And the way you play with the privacy wands is like the Dance of the Seven Veils. Thank you for occasionally dropping a crucial one.