MUPs were designed by idiots so it is no surprise people using them often behave like idiots. Pedestrians on MUPs are unpredictable so it is best to pass them very slowly even when you think you have their attention. It is sort of like car doors - when you get doored the person opening the car door is 100% at fault but you are still an idiot to ride in a door zone at speed because it is entirely predictable that sooner or later someone will open the door in front of you. MUP stands for Many Unpredictable People.