As Michael Hebb, the Seattle-based artist who founded “Death For Dinner,” puts it, “This is what the table does well. It’s a good place to have difficult conversations.” Participants like Laura Sweet, who hosted a dinner party on her apartment building’s roof, are finding that frank conversations about death can be refreshing and enlightening. As she put it, “people hesitated to leave and said they could talk about this for days. I don’t use the word magical much, but this evening was.”