Everybody’s an art critic. Especially if your art is covering an interstate highway sign. Last week, WW studied Portland’s seeming inability to wash off or paint over the graffiti that covers buildings, bridges and train yards all over town (“Spray Anything,” Jan. 31). Among our findings: Most of the taggers are just passing through, and washing off a highway sign removes the coating that lets it reflect headlights. Here’s what our readers had to say: