Most Karma is five stars. We all know that what that means - it could be anything from 'satisfactory' to 'amazing' and that's fine.
We all know what one star Karma means. It's something which does not breach the Terms Of Service (TOS) but destroys the session. So, for example, somebody not turning up and not sending a message. Not as rare as we'd like to be. (If the TOS are breached then the person should be Reported to the Moderators. In more serious cases the police should be involved.)
Two, three and four star Karma is relatively uncommon. There are obvious social reasons for this, but my feeling is that part of the reason is that nobody really knows what it means. What kind of situation warrants one of these intermediate ratings? Have you ever given or received such a rating: what was the story?
And no, I haven't had a curious experience recently - this is a purely theoretical question!