I agree. Other than the packages, name-your-own-price, and identified "special" fare deals mentioned above, we've had zero reports of purchases from Orbitz, Expedia, Travelocity, etc. not getting full MQM credit. People are getting hung-up on the fact that they are third parties, but are missing the fact that these are published fares which is the main criteria.
Let's be fair, we've had more than zero reports even booking on Delta.com, and At least 1-2 OTA-booked tickets I think. It's not foolproof.