Anna Sale fills in for Leonard Lopate. On today’s show: reporter Mark Follman explains how the popular online forum Reddit has become a gun marketplace. Isabella Rossellini talks about adapting her Sundance Channel series, “Green Porno,” for the stage. One woman shares her story of growing up as a Muslim in America. Plus, our word maven Patricia T. O’Conner takes your calls and questions about the intricacies of the English language.