I hadn’t gotten into that much detail with my post, but Mormon style polygamy is problematic, even when not practiced by the fundamentalist breakaway groups. This is in contrast with polyamory, which seems to be more egalitarian in nature.
One of the difficulties in attempting to separate the abuses which are the result of plural marriages from those which derive from being a member of a controlling, abusive cult is that there are parts of Mormonism, especially the fundamental aspects, which many people consider to be cult-like. People drawn to polygamy are those who extoll rigid patriarchy.
Mormon polygamy is not limited to members of the various breakaway branches, but also includes a number of independent adherents.
Because the main LDS Church has never disavowed the doctrine of polygamy, as conservative members start to dive into the deeper teachings of the church, some people become converted to this lifestyle, either by their own research or through other polygamists.
Mormonism is all about the afterlife, and the religion’s raison d’etre is its role in allowing only its members to achieve eternal salvation. The purpose of the ubiquitous Mormon temples are to perform rites which seal families together in the afterlife. These secret rites were born in as a cover for founder Joseph Smith’s hidden polygamous marriages.
Mormonism has so many aspects of patriarchy, but one example is that traditionally Mormon men were resurrected by the power of God, but women needed to be called by their husbands to join them in the afterlife. While not all women completely accepted this doctrine, those who agreed to polygamy would be more likely to.
Even in mainstream Mormonism, the power of men is unequal. After an LDS temple marriage, which is supposed to bind the couple together in both this life and after, a temple divorce is difficult to obtain. Without the temple divorce, the couple is still married in the afterlife, even if they remarry other partners, and even have children with the new spouses. Those children would belong to the original husband, and the second husband would have nothing.
Because the principle of polygamy has not been disavowed by the Church, this means that a divorced husband can get married again in the temple to another woman and would be married to both the new wife and the ex-wife for all eternity. OTOH, the ex-wife cannot enjoy a temple marriage and can only have a temporal marriage, and any children would go to the ex-husband. Traditionally, temple divorces were difficult to obtain, and husbands have extracted demands in exchange for their cooperation.
This seems similar to the points that @puzzlegal makes about the Orthodox Jews, although Mormonism doesn’t technically have the man “owning” the woman, just that he holds the key to her eternal soul.
