If its just about friendly bumping, half of cRPG´s cav players should be permabanned.That´s that.
Much better.
For riding a horse you should have to get a "riding license."
You'd have to go through an obstacle course, answer question etc. Every two weeks.
The obstacle course would consist a heavily populated area where the rider has to get from point A to B, without bumping anyone.
If you bump one guy, fine. But bump 2 or 3, and oops, no license.
I know, stupid suggestion is stupid. But it sounds funny.