I'm in love with this Horace, and you've convinced me that he has been horribly misunderstood by his original creator and by many of the authors who've borrowed him since.
His subtle understanding of the ways of the world and his ability to harness that knowledge is just perfect, and (with your brilliant observations via Flitwick) one can easily picture an Irma who appreciates this and is just as canny in her own way.
And the unexepected sweetness at the end! And the wry voice talking to that very dead sly dog of a headmaster! Who, Horace shows us, was never quite as clever as he thought himself.