1. The Eighth Ecumenical Council is the Council of 869-870, not the Council of 879-880. The Eighth Council was the one under the following five patriarchs:
1. Pope Adrian II of Rome (867-872)
2. St. Ignatius of Constantinople (847-858, 867-877)
3. Michael I of Alexandria (860-870) – represented by Deacon Joseph [Mansi XVI:190B]
4. Nicholas II of Antioch (860-879) – represented by Metropolitan Thomas of Tyre [ibid.]
5. Theodosius of Jerusalem (862-878) – represented by Presbyter Elijah the syncellus [ibid.]
2. The following 26 Eastern metropolitan bishops signed the Acts [Mansi XVI:190C-191D]: Thomas of Tyre, Basil of Chalcedon, Nicephorus of Amasya, Basil of Gangra, Nicephorus of Nicaea, Cyprian of Claudiopolis, John of Perga, Stylianos of Neocaesarea, Theodore of Thessalonica, Nicholas of Myra, Sisinnius of Laodicea, Nicetas of Athens, Nicholas of Synnada, Stylianos (a.k.a. Theophylactus) of Iconium, Hilary of Corinth, Michael of Rhodes, Ignatius of Hierapolis, Euthymius of Larissa, and Metrophanes of Smyrna.
3. Pope John VIII of Rome of pious memory (872-882) did not annul the Council of 869-870. Daniel Stiernon [Autour de Constantinople IV (869-870), p. 180] points out that nowhere does Pope John VIII, in his genuine (i.e., unmodified) letters, abrogate the 869-870 Council, and he cites [n. 148] Fr. Venance Grumel, A.A., “Les lettres de Jean VIII pour le rétablissement de Photius,” in Echos d’Orient, XXXIX (1940), 138-156. Stiernon also stresses [Autour de Constantinople IV (869-870), p. 176] that in the pope’s genuine letter to Byzantine Emperor Basil I the Macedonian [MGH, Epist., VII, 169), Pope John VIII cites canon 68 of the 419 local Council of Carthage [Mansi III:771E], which reads:
not that the Council which met about this matter in foreign parts should be done away, but that it may remain in force with regard to those who so will to come over to the Catholic Church that there be procured by them no breaking of unity… there shall not be objected to them the decree contrary to their honor adopted by a foreign council, for salvation is shut off to no one, that is to say, that those ordained by the Donatist party, if having been corrected they have been willing to return to the Catholic Church, are not to be received in their grades, according to the foreign council; but they are to be excepted through whom they received the advice to return to Catholic unity.”
4. Moreover, the letter of Pope Stephen V of pious memory (885-891) to Emperor Basil I in 885 or 886 proves that no pope annulled the 869-870 Council, since Photius, who nonetheless died in the odor of sanctity, was still, at the time, trying to have the former council abrogated. See Fr. Grumel’s “La Lettre du Pape Étienne V a l’empereur Basile Ier” on pp. 129-136 of the 1953 edition of Revue de etudes byzantines; the letter, according to p. 137, is from the manuscript Sinaiticus gr. 1117, 326v-328v. Fr. Dvornik of pious memory did not address this even in the 1970 edition of his monumental work, The Photian Schism.