LE MUR seems to be very upset with MTO experiment. Whereas people invited to Le Mur try to make a good looking wall. MTO asked a black wall, and a QR code brought by a tramp at the opening invited people to write on it for the next 2 weeks. MTO abandoned the billboard to the people and has written words & tags in the streets around.

The whole explanations with e-mails between MTO & Le MUR here (in French).
The saddest part is that 2 days later, Le Mur ordered this painting…