"I am sure audiences can tell the difference between good and bad singers the point is they clap for everyone because they are well mannered, which is really what this thread started out discussing."
   no , they do not clap equally that is not true, in fact some audiences have been known to walk out of Vin Garbutt Concerts in the past, some members of the audience have stayed but not applauded, likewise some people do not clap fox hunting songs and some come up and talk to the singer about the subject in the break, no audiences vary very much.
in my experience audiences[and i have attended folk venues since 1965] do not clap equally for every song, i remember one man calling out judas to bob dylan