Oh Kendall - do tell...
I personally can't abide slavish repetition - I think a song (and equally this applies to stories being told) should be sung from the heart and will therefore vary in many small ways each time it is sung - that is what keeps a song fresh for me.
The verb "Plausiblisation" was invented for me by friends who at the time prefered to learn the exact tunes from CDs. I always sounded as though I might be singing the right tune - but seldom was.
That's why I mostly sing alone now...... :>)
At a session the other day the organiser turned to me after I had sung The Snow It Melts The Soonest, and asked (somewhat sceptically I thought)whether that was the right tune. I nearly fell into my drink, and replied faintly that I seriously doubted it!
I'm not averse to messing with the words & combining bits & pieces either - hence I was able a couple of weeks back to introduce "Come Kiss Me Love With Bits Of Peggy Gordon And Some False Young Lover".
I passionately believe in taking the original as a starting point from which to diverge a little or a lot according to your fancy. I know that's not a universally held view though.
I don't think I've ever sung anything in front of its writer yet - I think I'd have to throw myself on their mercy.

Kris