For the 2016 election, the ABC Vote Compass has a diagonal bias embedded in some of the questions, reinforcing the major party axis and making it impossible to score highly (or lowly) in both economic freedom (Economic Right) and social freedom (Social Progressive) at the same time.
Due to the structure of the questions, final results are only possible within the shaded area, and can never reach the top right or bottom left corners.
EDIT (2016-06-23): It is possible to get in the top right (or bottom left) by answering "Don't Know" (rather than the middle answer) to the six diagonal questions. Results are scaled to only the questions you answer (this also scales the position of the parties to those same questions). The limitation applies if you answer every question. Also, the actual limit is slightly curved (not a straight line), as each question has a slightly different economic/social ratio, so it is actually possible to do slightly better than all-neutral answers.