The Underground Man lacks any sort of social skills. It is his lack of understanding the cues that his classmates give him which cause the social akwardness. Had he not invited himself to the diner, he would have been able to avoid the ridicule from the other men, and been able to complete his responsibilities. The Underground man is defiant, ignoring the signals that the classmates give him to leave/improve the condition of the diner. He lacks all social graces and makes everyone uncomfortable in the setting.