I remember in 65 or 66 going on an expedition to the Bell in Standlake(Oxfordshire) to meet some locals for a session(including Aubrey Cantwell, the man from whom the "they kissed so sweet and comforting" Nightingale was collected). Anyway, the organiser of the trip asked me not to bring a guitar, as it wouldn't be traditional! I have come to the conclusion since then that Aubrey would not have minded the presence of a guitar in the least. But at least it prevented me from attempting to back him on the Nightingale, which would have been too embarrassing for me to contemplate now.
Another, rather different incident:probably at a Cambridge Folk Festival session, also probably 65 or 66. I was playing some clawhammer type guitar thing, and at the end this bloke(who also had a guitar) said "Was that right, what you were playing?". So I said, as you might, well I dont know about right, there were probably a few bum notes, and he said, with more emphasis"No, was it right?". Then I sort of clicked, and he sort of explained. What he meant was, was this a faithfully transcribed piece off Mississippi John Hurt or Blind Blake or Elizabeth Cotten or whoever. So I had to admit, no it wasn't right, I was just playing my own version of whatever it was. At which point, he very rightly lost interest!