DANVILLE — Under the cover of darkness, the Iron Horse Trail is an easy place to post anonymous, antisemitic flyers. In daylight, the well-traveled rail trail provides a bevy of eyeballs for the hateful messages that have been cropping up in the Bay Area. But the high traffic in places like the Iron Horse Trail, which runs more than 30 miles between Concord and Pleasanton, may also speed up the removal of such flyers. That’s exactly what Tom Maneloveg did last weekend when he spotted a colorful paper pinned to a pole while on one of his frequent early morning...