Harry is, on the surface and...for the most part beneath the surface, a very nice man. And he really, really likes building things. Things the world is not ready to see or want. At least not the everyday world. Prometheans, however, are more than happy to see what he has to build. So long as it benefits them in some sort of way. He's totally fine with that. For the most part.
If jittery or overly enthusiastc were personality types, then they would describe Harry Feynman. (Jittery is now a personality type)
He's autophobic, meaning the idea of isolation, of being alone absolutely petrifies him. And yet, he lives alone in a large home with a revenant in the basement. Occasionally his sister may or may not visit. Occasionally his father tries to get control over his life. And the finances he worries Harry is giving away willy-nilly. These things rarely last.
But yes. Harry? Super nice! That said, he knows how to make a sale of his weird and wacky inventions that no one really needs except they do. Because he said they do. The same goes for the books he sells in his shop. Because he says so. And he's rarely wrong.
Harry likes everybody, pretty much.
He's smart, our Harry. This does, at times, come out at inappropriate and strange times. Like in lists. Or all over the walls of his office or home. But these things are easily covered up by wallpaper, aren't they?
Harry is about six feet tall and as skinny and muscular as a rake. But that's okay, that's fine. There are plenty of other ways to fight. If he must.