Not meaning to drag up an old thread, but I have read most of what has been written on the forum regarding the "Sacred Heart of Jesus" in Catholic devotion, and what I have not seen brought up is the whole issue of the purported visions involving it. This is from Wikipedia:
"On December 27, probably 1673, the feast of St. John, Margaret Mary reported that Jesus permitted her, as He had formerly allowed St. Gertrude, to rest her head upon His Heart, and then disclosed to her the wonders of His love, telling her that He desired to make them known to all mankind and to diffuse the treasures of His goodness, and that He had chosen her for this work."
"In probably June or July, 1674, Margaret Mary claimed that Jesus requested to be honored under the figure of His Heart of flesh, also claiming that, when He appeared radiant with love, He asked for a devotion of expiatory love: frequent reception of Communion, especially Communion on the First Friday of the month, and the observance of the Holy Hour."
"During the octave of Corpus Christi, 1675, probably on June 16, the vision known as the "great apparition" reportedly took place, where Jesus said, "Behold the Heart that has so loved men ... instead of gratitude I receive from the greater part (of mankind) only ingratitude ...", and asked Margaret Mary for a feast of reparation of the Friday after the octave of Corpus Christi, bidding her consult her confessor Father Claude de la Colombière, then superior of the small Jesuit house at Paray. Solemn homage was asked on the part of the king, and the mission of propagating the new devotion was especially confided to the religious of the Visitation and to the priests of the Society of Jesus."
Regardless of the apologists defending the devotion by claiming that it represents Christ's Divine love, as an Orthodox Christian I cannot, and do not, accept the validity of these visions, anymore than I accept the countless other visions that Catholics have claimed to support questionable devotions.
I do not believe our Lord appeared to this Nun and spoke these things.