Originally Posted by SweetBerry

Airlines can definitely divorce the segments, but that depends on whether they are willing to.

GDS do have mechanisms that prevent agents ticket MSC segments separately beforehand.

I'm not sure if it's actually Married Segment causing it. Confused agents can think it's an entire international itinerary (because everything is under one PNR and they see that, even though there are two tickets) and they want to check-in to the final destination with luggage and documents. How long is the time between domestic segment and international segment? If it's not overnight, I can guess the check-in agent just think it's an international itinerary and they don't want to short check