A remark on a Protestant blog brought to mind the fact that schism is really an impossibility on the terms of the Reformed Protestant. In the first place, one who is “elect” can never, ever leave the “invisible church,” just by definition. And in the second place, no visible ecclesial community has any real authority over the Christian that isn’t trumped by his own personal appeal to the Bible. Since (on the Calvinist’s erroneous reading of things) both churches and councils can and do err, the Christian’s appeal to the Bible is the final court of appeal for him. On what grounds can an ecclesial court (to say nothing of individual Calvinists) call a man “schismatic”? Any such accusation is purely and solely ad hoc.
And maybe most importantly: it would be grossly hypocritical. Either it is no sin, or Luther and Calvin were schismatics and their whole revolt was illegitimate. So I don’t see how a Reformed Protestant can ever consistently call schism a sin.