"Or in fine, in the first place they were on the same standing with their brethren; thus this holy calling being prepared from the foundation of the world for such as would not harden their hearts, being in and through the atonement of the Only Begotten Son, who was prepared— And thus being called by this holy calling, and ordained unto the high priesthood of the holy order of God, to teach his commandments unto the children of men, that they also might enter into his rest—"
So there wasn't some great advantage for these people who hold actual priestly authority. We learn that "in the first place they were on the same standing with their brethren." Where was that "first place?" Is it also "from the foundation of the world" referred to earlier?
What does it mean that they were "on the same standing with their brethren" while in that first place?
What was it about these who receive authority that qualified them to receive the "holy calling" from the foundation of the world? What does it mean that they "would not harden their hearts" in the first place? If they didn't do it then, will they do it now?
Is foreknowledge about these individual's qualifications based on prior performance? Can you determine that since they did not harden their hearts in the first place, they will not begin to harden their hearts now?
What about the "atonement of the Only Begotten Son, who was prepared" made them qualified? Did they accept Him there? Did they soften their hearts there toward Him? Are they capable of having redeeming faith in Him here because they first acquired it there?
Is all this necessary to have preceded ordination here? If it was not acquired there, can an ordination here have any effect?
What, then, do those who qualify do? What does it mean "to teach his commandments unto the children of men?"
Is there something different between teaching commandments on the one hand, and "that they [who are taught] also might enter into his rest" on the other hand? Are the two linked together? Is it necessary to both "teach his commandments unto the children of men, that they also might enter into his rest" to show such priestly authority? That is, can anyone, regardless of their true ordination to authority teach commandments? But does it take something more, some higher ordination in order to bring those taught "to enter into His rest?" If so, what is the difference? How can you recognize such teachings if they are ever put on display?
Did Joseph Smith exhibit such powerful teachings?
Did Melchizedek? Abraham? Elijah? Elisha? Nephi? The Brother of Jared? Enos? Others?
Do we see that today? If so, where? Does anyone have the audacity to presume they can bring another soul back to the Lord's rest? Maybe Joseph Smith's comment on this point is appropriate: "“The things of God are of deep import and time and experience and careful and ponderous and solemn thoughts can only find them out. Thy mind O man if thou wilt lead a soul into salvation must search into and contemplate the darkest abyss and the broad expanse of eternity, thou must commune with God.” (DHC Vol. 3, p. 295.) I'd like to meet such a man. They seem to be rather infrequent residents of this fallen world....
I'm only asking those questions which arise in my own mind as I read these words. You'll have to figure out your own answers.