Looks are deceiving. Karen Buchholz, right, Comcast’s senior vice president of administration, seems to be talking on one of the higher floors of a Philadelphia office building. But she’s really standing in the company’s “mock-up” for its new tower on the first floor of a suburban corporate office. The mockup, a nearly perfect replica of a quarter of a floor in the new tower, is designed to show employees what it will be like to work in the new building.