Yes, I learned about the Arab Christian tradition concerning Mohammed being a Christian missionary who went rogue, when I mentioned the German scholarly findings at coffee hour after Liturgy a few years back. Both a Copt and a Rum Orthodox from Jordan were quite insistent that they had always heard that Mohammed had started as a Christian missionary.
In the case of the Copt, a cynic might think attaching him to the Church of the East might be anti-Nestorian bias, but the Rum Orthodox (that’s what us Eastern Orthodox are called in the Middle East) learned the same tradition, and it’s supported by the linguistic analysis (passages of the Qu’ran being nonsensical Arabic, but perfectly good East Syriac).
Interesting. If true, that would mean that, when Belloc called Islam a Christian heresy, he was exactly right.
Very interesting. Incidentally, what’s the derivation of “Rum” Orthodox? Is it related to “Rom,” as in “Roman,” as in the Empire (Constantinople)?