Yeah, I've been playing around on delta.com with multi-city segments, and one-way options, etc to see what I get.
In one Multi-city segment with the same itinerary, I got L fares going to IAH, and L fares on the return. I tried to book it, and it said "sorry those segments are no longer available"...searched again 20 seconds later, and got K going to IAH and L coming back to MCO and $100 higher. Checked on my workstation, and it's now L going to IAH, and K coming back to MCO. EF shows K going there, and L coming back.
The Benny Hill Show going on over here with delta.com.