Grief can be eased by deliberately erasing the things that tie the living to the dead: burning their belongings and house, no longer saying their name, and changing the look of places they used. In this view, recovering from loss means loosening memory's grip rather than preserving it.
Where people believe personality and individuality live in the body itself, the corpse becomes the most powerful reminder of the dead person. Transforming the body is then a way to transform the survivors' memories and help them let go.
One outward act can carry opposite meanings depending on who it is done to and why. Eating slain enemies expressed anger and contempt, while eating one's own dead expressed affection and respect and helped the bereaved cope.
What feels most repulsive is set by culture, not nature. Leaving a loved one's body to rot in the ground was as horrifying to these people as eating human flesh is to outsiders, so consuming the dead could seem the most honorable and loving choice.