Berlin is a city full of graffiti: Colorful and loud, imaginative, annoying, and often political. Spray paint seems to have long since conquered the city. Yet on April 11 this year, three large words sprayed across the side of a building in the district of Prenzlauer Berg, calling in English for the killing of all Jews, provoked outrage and shock.  The words were quickly covered and then painted over — yet the message still shows through if you look closely (top photo). True to Berlin's character, civil society responded: Residents held a vigil. Blue‑and‑white ribbons now hang from lampposts and traffic signs, bearing the words "Against all antisemitism " beside a Star of David.…