It is purely Munchkin.
Unless the GM gives them to you as campaign background, Limitations and Complications are picked by the player but they only come up if the GM puts them into the story.
If they don't come up, you got points for free.
Selling back Characteristics/Movement gets you points. If you got points, it should come up and should be as frequent as the equivalent point value in Limitations or Complications. Otherwise, points are being taken for free.