...the official church stance on Bernie Sanders' democratic socialism

Some have suggested that the practice of the law of consecration and the system of the united order are only a religious kind of socialism or communism. Others assert that it was a development either from the economic philosophies of Joseph Smith’s day or from communal experiments within the new religion. Such assumptions are false. The Prophet Joseph Smith attended a presentation on socialism in September 1843 at Nauvoo. His response was to declare that he “did not believe the doctrine” (History of the Church, 6:33). In more recent times Elder Marion G. Romney outlined the differences between the revealed system of the united order and the socialistic programs:

“(1) The cornerstone of the United Order is belief in God and acceptance of him as Lord of the earth and the author of the United Order.

“Socialism, wholly materialistic, is founded in the wisdom of men and not of God. Although all socialists may not be atheists, none of them in theory or practice seek the Lord to establish his righteousness.

“(2) The United Order is implemented by the voluntary free-will actions of men, evidenced by a consecration of all their property to the Church of God.

“… Socialism is implemented by external force, the power of the state.

“(3) … The United Order is operated upon the principle of private ownership and individual management.

“Thus in both implementation and ownership and management of property, the United Order preserves to men their God-given agency, while socialism deprives them of it.

“(4) The United Order is non-political.

“Socialism is political, both in theory and practice. It is thus exposed to, and riddled by, the corruption that plagues and finally destroys all political governments that undertake to abridge man’s agency.

“(5) A righteous people is a prerequisite to the United Order.

“Socialism argues that it as a system will eliminate the evils of the profit motive.

“The United Order exalts the poor and humbles the rich. In the process both are sanctified. The poor, released from the bondage and humiliating limitations of poverty, are enabled as free men to rise to their full potential, both temporally and spiritually. The rich, by consecration and by imparting of their surplus for the benefit of the poor, not by constraint but willingly as an act of free will, evidence that charity for their fellowmen characterized by Mormon as ‘the pure love of Christ.’ [Moroni 7:47.]” (In Conference Report, Apr. 1966, p. 97.)

President J. Reuben Clark Jr. said: “The United Order has not been generally understood. … [It] was not a communal system. … The United Order and communism are not synonymous. Communism is Satan’s counterfeit for the United Order. There is no mistake about this and those who go about telling us otherwise either do not know or have failed to understand or are wilfully misrepresenting.” (In Conference Report, Oct. 1943, p. 11.)

President Marion G. Romney warned about the continuing imitations of the adversary: “In this modern world plagued with counterfeits for the Lord’s plan, we must not be misled into supposing that we can discharge our obligations to the poor and the needy by shifting the responsibility to some governmental or other public agency. Only by voluntarily giving out of an abundant love for our neighbors can we develop that charity characterized by Mormon as ‘the pure love of Christ.’ [Moroni 7:47.]” (In Conference Report, Oct. 1972, p. 115; or Ensign, Jan. 1973, p. 98.)

President Romney noted:

“I suggest we consider what has happened to our agency with respect to … government welfare services. …

“The difference between having the means with which to administer welfare assistance taken from us and voluntarily contributing it out of our love of God and fellowman is the difference between freedom and slavery. …

“When we love the Lord our God with all our hearts, might, mind, and strength, we will love our brothers as ourselves, and we will voluntarily, in the exercise of our free agency, impart of our substance for their support. …

http://acalltoarmz.blogspot.com/2015/03/is-united-order-christian-communism.html
https://www.lds.org/manual/doctrine-and-covenants-student-manual/enrichments/enrichment-l-the-law-of-consecration-and-stewardship?lang=eng&query=communism