Wow...five posts in a row? Dude, it's called summarizing your thoughts. Sounds like you like Orbitz, and something about the segments and fare rule loopholes is generating the lower fares. There, I'm done addressing OP's question, except now I feel the need...
As someone else said, no reason the OP couldn't book the lower fare AND ALSO complain to Delta to possibly get some miles. Seems that you're familiar with the
complaints about DL.dumb.
The correct name is
Economy Comfort, and it is officially available on domestic flights beginning June 7. Beginning a couple weeks ago,
anyone with a post-6/7 flight booked could purchase themselves an EC seat directly through DL.com, just like they have been for international flights for some time. You do not need to use an agent, DL, Travelport, or otherwise, though I assume you're certainly welcome to.
We.
Get.
It.
OTA websites will often find loopholes (the A-B + B-C < A-B-C example earlier), whereas carrier website will always try to play by the "rules" (you want to get from A to C, you pay the fare designed to compete with the A to C market).
But to be clear, OTAs that use direct searches of (almost) realtime inventory generally ought to be displaying the same seats and fare buckets as those available directly through airline websites, albeit in potentially different combinations. This is the main gripe with airline websites, which carry "Best Fare Guarantees", not showing the lowest possible price.
Of course, the exception to this would be consolidator fares, and the caveat to that would be that
you should understand when you are and are not seeing them.