It states in the article that he has (or has been diagnosed with) post-traumatic stress disorder. If you care to look at Wikipedia, among the diagnosis criteria is "F. Significant impairment in social, occupational, or other important areas of functioning". So, I imagine the cat, when the article says that it functions as a "social buffer", means that he feels more comfortable in social situations when the cat is around.
It states in the article that he has (or has been diagnosed with) post-traumatic stress disorder. If you care to look at Wikipedia, among the diagnosis criteria is "F. Significant impairment in social, occupational, or other important areas of functioning". So, I imagine the cat, when the article says that it functions as a "social buffer", means that he feels more comfortable in social situations when the cat is around.