Jocoseriosity: half-joking, half-serious, like this blog.
How many times have you hear someone speak with jocoseriosity? He makes his point with a slight spice of humor, and half the audience loves it, the other half hates it. Both remember it, so the jocoserious speaker wins.
Good word. Seriosity on its own is pretty good too. Woody Allen used “jejunosiousness” in one of his movies, I think.