It is one thing for something to be inspired or revelatory and therefore scriptural, and another for it to be canonized and become binding on the members of the Church—meaning their lives and conduct will be judged by the content of the scripture. The four standard works of the Church are canonized scripture; what is said under the influence of the Holy Spirit at General Conference is true and timely/relevant counsel, but is not canonized scripture, binding on the members. These are distinctions that seem to be lost on some members (and most non-Mormons) but would be helpful to all if understood.
From Determining Doctrine:
From the Doctrine and Covenants:
And, behold, and lo, this is an ensample unto all those who were ordained unto this priesthood, whose mission is appointed unto them to go forth—
And this is the ensample unto them, that they shall speak as they are moved upon by the Holy Ghost.
And whatsoever they shall speak when moved upon by the Holy Ghost shall be scripture, shall be the will of the Lord, shall be the mind of the Lord, shall be the word of the Lord, shall be the voice of the Lord, and the power of God unto salvation. (D&C 68:2-4.)
Bruce R. McConkie:
Anything spoken by the Father, Son, or Holy Ghost, by the angels of heaven, or by mortal man when moved upon by the Holy Ghost, is scripture. Such spoken words are the will, mind, word, and voice of the Lord. (D.&C. 68:1-5.)
Since it is a comparatively rare thing for mortal man to hear the personal voice of Deity, or to converse with angels, it follows that most scriptural utterances are given to man by revelation from the Holy Ghost. These statements, made by the power of the Holy Spirit, consist of the identical words which the Lord himself would speak under the same circumstances. They are indeed the Lord’s words because he authorizes and directs the Holy Ghost to influence and guide men in giving utterance to them.
It is by the power and guidance of the Holy Ghost—that Spirit Personage who, as a member of the Godhead, has power to speak with unerring certainty to the spirit within man—that the saints “have the mind of Christ.” (1 Cor. 2:16.) That is, when moved upon by the Holy Ghost, the saints are enabled to think what our Lord thinks, to give voice to the very words he does or would speak, and to act as he would act in the same situation. What is true of the mortal saints is also true of the heavenly saints, for “Angels speak by the power of the Holy Ghost; wherefore, they speak the words of Christ.” (2 Ne. 32:32.)
All scripture is true. It is composed wholly and solely of pure, unvarnished, irrefutable, and eternal truth. “Thy word,” O God, “is truth.” (John 17:17.) “By the power of the Holy Ghost ye may know the truth of all things.” (Moro. 10:5.)
All scripture comes by revelation. Whenever any revealed truth is expressed in words, those words are scripture. “The Holy Ghost is a revelator,” Joseph Smith said, “No man can receive the Holy Ghost without receiving revelations.” (Teachings, p. 328.) And when those revelations are either spoken or written, they are scripture.
Most scripture has been, is now, and will continue to be oral and unrecorded. Throughout the length and breadth of his earthly kingdom, the Lord’s agents are frequently moved upon to speak, testify, prophecy, exhort, expound, preach, and teach by the power of the Holy Ghost. Such inspired utterances benefit and bless those who speak them and the spiritually endowed among the hearers. (Mormon Doctrine, p. 614.)
(Quoted in Doctrinal New Testament Commentary, 3 vols. [Salt Lake City: Bookcraft, 1973], 1:55-56.)