Complex sentence: Many commentators have noted that John avoids saying whether Thomas actually did "thrust" his hand in, but the usual belief before the Protestant Reformation was that he did, which most Catholic writers continued to assume, while Protestant writers often thought that he had not.
Split into simpler sentences: Many commentators have noted that John avoids saying whether Thomas actually did "thrust" his hand in. Before the Protestant Reformation the usual belief was that he had done so, which most Catholic writers continued to assume, while Protestant writers often thought that he had not.