Generally, it is agreed that Christian mythology is on-topic. Now, recently, there has been a great deal of discussion in chat about how to distinguish "genuine" mythologies (e.g. Greek, Norse, Native American, etc.) from "fictional" mythologies (e.g. Star Wars, Game of Thrones, etc.). Various criteria have been proposed, including age, creative intent, and temporal separation from modernity. Previously, Cthulhu was deemed off-topic and Scientology might be on-topic. durron597 and I don't really care much about Scientology either way. This chat discussion spawned this Meta question, and my question seeks to bring up another example that might be off- or on-topic and the consensus will hopefully help us (the community) come up with a definitive answer to that question.
Scientology is a gray area. Mormonism, however, is an unknown-color area. It's recent, but the sacred texts are intended to be corrections and additions to the classic Bible. For instance, Doctrine and Covenants records the revelations of their Prophet Joseph Smith.
As an example of Mormon mythology, there is this Christianity.SE question: Did Noah build the Ark in America? The original poster included links to verses that show that Mormons believe that Eden was in Missouri, a state in the United States of America, which is half a world away from its traditional location in the Middle East. They also show that yes, the Mormons did believe that Noah built his Ark in North America.
The orthodox, Judeo-Christian stories of the Garden of Eden and Noah's Ark are certainly considered to be mythology that is on-topic for this site. What about Mormonism's recent version of the same events?