There are two sources for the title of the show. The first is the text at the beginning of the first episode, where it describes the psychology of some of those without cybernetic implants. Essentially, they have a "Stand Alone Complex"; they feel that they "stand alone" from the rest of humanity who have cybernetic implants, which allow those with them to communicate at any time with anyone who also has implants. The second source is a reference to the story itself. The term is used to describe an event where multiple people who have no associations with each other and are not part of a common group(thus they "stand alone"), through similar actions, seem to work together towards a common goal. This "complex" is referenced a number of times in the story, mainly about the laughing man case, but also in reference to a few other cases the group encounters.
There has never been reported stomach aches or related medical trauma that takes place after swallowing your pride.