On Wed, 23 Jun 1999, Andrew Carey wrote:

     Okay... what is "weird" about poly relationships?  This is Ranma 
1/2--we have water-activated curses, engagements made in exchange for meals, 
and schoolyard melees of forty against one.  These things are not "weird," 
but a loving relationship between more than two persons is?

There's a difference between having weird physical laws and weird customs,
and making human nature weird.

Besides, there's an element of possessiveness to all the girls' attempts to
get Ranma.  Even Akane gets jealous when she sees Shampoo glomping Ranma;
polygamous relationships are out of character for everyone.  One doesn't just
throw in a major piece of mischaracterization into a fic for no reason other
than it sounds neat.