That's a rather vague question. If you have a specific question on MD-80, MD-11, MD-90, MD-95, or MD-10 perhaps I could answer it as I had some involvement with the development of all those types.
All of the MD commercial aircraft were designed by Douglas Aircraft Company, Long Beach. Boeing had no involvement with the design of any of them although they did re-name the MD-95 to B717 and did send a few people down from Seattle for the flight test program.
You have to get down to specifics e.g, If AP is engaged in ALT HOLD mode in cruise, and available engine thrust is insufficient to maintain altitude and keep airspeed above stall speed, what should the AP do? The choices are 1) lower the nose and maintain safe airspeed or 2) maintain altitude until stall. This was debated with strong opinions for each answer. Douglas decided AP should maintain altitude and allow the aircraft to stall. What label do you put on that design philosophy?