I disagree. A schism is never legitimate. If it was, there would be no schism. Schism's are always looked at as heresy by the other side. That's what makes them fun, interesting, and that's why the winner determines who was the true heretic.
Which is why there is an obvious orthodox, non-heretical, non-schismatic form of Islam or Christianity.
No; schism's are defined by the presence of 2 factions with strong legitimizing claims and strong political power. And usually schisms don't end with one side winning. The only demographically major schism of a major religion I can think of where one faction has well and truly died is Arian Christianity; but I'll admit I'm not extremely well versed in Hindu and Buddhist history.
