Dear Forest, every election method that meets the majority criterion is vulnerable to "compromising". In so far as a voter will usually approve at least that candidate who gets this voter's first preference, you cannot circumvent this incompability by using "some hybrid method that requires information outside of the pairwise comparisons, perhaps information not available in preference ballots".
Example: 40 A > B > C. 35 B > C > A. 25 C > A > B. Suppose that the used election method meets the majority criterion. Suppose that A wins the elections. Then the 35 BCA voters can change the winner from A to C by voting CBA (i.e. by "compromising"). Suppose that B wins the elections. Then the 25 CAB voters can change the winner from B to A by voting ACB (i.e. by "compromising"). Suppose that C wins the elections. Then the 40 ABC voters can change the winner from C to B by voting BAC (i.e. by "compromising"). Markus Schulze
