Is there anything wrong with wanting to stop time? Debora L. Spar thinks the question is more complicated for feminists of a certain age. In an essay titled “Aging and My Beauty Dilemma,” published over the weekend, Ms. Spar, the president of Barnard College, argues that the way women are expected to look at 40, 50 or 60 is at odds with nature and, in certain cases, their values. Below are some of our readers’ responses from letters and Facebook comments, edited for grammar, style and space.