Is it really possible to marry a university sim?

Definitely possible. I've married a University Sim numerous times. I had a hiccough with one, Jeffrey Deane, but married Eddie Muller numerous times and never had an issue. I'm glad they made this possible as it gives more variety to you sims background story. As above though, if you're wanting to get married and start a family actually in the university world, that's not possible. I wouldn't even do it with mods as I'd worry it would seriously ruin something else.