"...audiences have the right to expect that an artist isn't enjoying themselves so much that it interferes with their ability to deliver the performance for which they are being paid and the audience is paying. I've been in the audience at another festival where artists excused a below-par performance by telling us they'd been out on the razzle the night before, and found it rather disrespectful and unprofessional."

Ruth - I couldn't agree more. But Moira hasn't said there was a below-par performance, or that their ability to deliver was impaired. I'm glad you'll check it out. But I hope you won't penalise a performer purely for a harmless bit of banter. I don't agree such banter in itself is unprofessional.