Poignant, touching, and in moments even philosophical, “Thirteen Conversations About One Thing,” Jill Sprecher’s sophomore effort, very much fulfills the promise she has shown in her 1997 Sundance-premiered debut, “Clockwatchers.” Interweaving five contemporary stories into a single narrative, the film deals with the profound, often unintentional impact that seemingly disparate people have on one another, while searching for a more meaningful and happier existence.