Constantinius, good catch. That’s an important point. An Orthodox or Catholic doesn’t decide to refrain from receiving in a Protestant church because he perceives important doctrinal differences. Rather, he submits to the discipline of his church and the judgment of his bishop, who is not in communion with any Protestant church. It seems to me that the doctrinal differences are a secondary rather than the immediate reason why I would not eat crackers and grape juice in the church I grew up in.