I suppose if you were recording a song that kind of thing would be appropriate. But when it comes to singing I think we're all free to do what seems right, within reason. I don't fancy sitting in song circle with someone going through a textual anaysis of the variations in what they are singing from the version collected back in 1910...

Point taken (I wouldn't fancy it, either, to be honest). It's the 'what seems right, within reason' that concerns me. We probably all have our own ideas of what that means. I just feel there ought to be some safeguard against someone completely rewriting a song to suit their own tastes - then the original author, should they hear it, might not be happy. And others hearing the revised version might attribute it to the original author. Depends on how well it's done, I guess.