Jim, there are occasions when it makes sense, particptory songs like shanties,of non narrative songs candlight fishermen, when a performer has good chorus singing going, do it one more time.
I talk from the point of view of a as a professional performer,not as a collector of traditional songs from traditional singers, all that concerns me as a performer is what works as a performer, I could not care a toss whether any other trad singer approved of it, they were frequently singing in different situations, that does not mean that I do not have respect for other aspects of unaccompanied traditional singers style, you are right, it is generally speaking a nonsense in a narrative ballad,here is a song where it would be a bit silly
Phil Tanner here
http://www.youtube.com/watch?v=0xVT-vdJL4g
The point about shanties is they can be of any length, they were work songs designed to last as long as the job took, as regards singing shanties in folk clubs they can last as long as they are doing the job of getting people to join in ,it is up to the performer to judge when enough is enough, as the actress said to the bishop.