The substance of the thread is about the performance, what is the "norm" by the performer, and what is expected of those who suport the performance.
As an example, was it not the Great Ralph McTell this year at Cambridge who basically had to ask the audience to let him do "HIS" version of Clare To Here, rather than let the audience lead the chorus in their version.
Here was an international artist having to request a fee paying audience to let him do the song his way !
Even in a local "Session" the "Lead" performer has a right to expect that people will let them do their own personal version, and accompaniests play along with that, rather than impose another verion of the song/tune on the "lead" performer.