I usually fall for beautiful, but hurting men. I don't think it co-dependent...it's normal for a woman to want to nurture and heal. Yet I agree with your comment about moderate individuals. As to why this happens, I'm learning....I'm perpetuating a cycle of defense mechanisms in order to avoid the potential of abandonment. Sometimes borderline females are attracted to borderline males with other disorders. It is a risk to be in love with a damaged person....if they have an inability to love you, they will hurt you.
Knowing when not to take the risk, even in love, is key for me.