It seems to me that (1) having one person sing and the rest listen, (2) having one person sing the stanzas and the rest join in on the refrain, and (3) having everybody sing the whole song are all legitimate, and have their own pleasures, and may reasonably be catered for at different sings or at the same sing. In cases (1) & (2) it is IMO pleasanter if the singer can do without a written text, but some singers can't, and I wouldn't want to tell them to shut up. In case (3) it is certainly nice if people can take cues from each other & not have their noses buried in books, but that requires a stable group & a limited repertoire, because with folksongs, almost by definition, people are going to come in knowing different versions, and some sort of agreement has to be arrived at. That is asking a lot in this age of high mobility. In a group where there are new people at every session, each with his or her own notion of the order of stanzas and the name of the narrator in "St James Infirmary Blues", RUS is IMO the lesser evil.