But the result would be even worse if nobody ever did. From a cost-benefit point of view, it would be better if they situated themselves at 0.25 and 0.75. That way the average distance walked would go down to 0.125. But that is not an equilibrium. Page 37 Pareto avoids inter-personal comparison, but cannot compare situations in which there are both gainers and losers.
Cost benefit takes into account preference intensity, and simply adds up utility among individuals.
All options are Pareto efficient, since any move would make at least one person worse off. All options are Pareto efficient, since any move would make at least one person worse off. Note that this assumes that candidates care about nothing else but their own election. When there is an odd number of candidates in one dimension, there is no equilibrium. Therefore there never is an equilibrium.