There is nothing to talk about this subject. You make it sound as if there is only one side to it. The reason why I omitted this was its a historical irrelevancy given that Petrine authority is at the heart of any controversy.
The RCC and EOC recognize two different 8th ecumenical councils” is historically interesting.
There was a council in AD 869-70, in which Photios was condemned and Ignatius I was confirmed as the legitimate Patriarch of Constantinople. Today Catholics accept this as an ecumenical council. This is what the Catholic Church called the Fourth Ecumenical Council of Constantinople or Constantinople IV, which is the eight ecumenical council, was held on AD 869-70.
In AD 879-80, there was another council, which reversed the first and declared Photios the lawful Patriarch.
The Orthodox hold this council of 879-80 as ecumenical, and declare the previous one to be a robber council. The Orthodox would like to think that this is the eight ecumenical council and that this council annulled the one held at AD 869.
Not so!
When Photius went bad, Pope John VIII, sent legates to Constantinople. A council was held there and Photius was condemned along with his errors [which he promulgated on a council in 867]. THIS IS “THE FOURTH ECUMENICAL COUNCIL OF CONSTANTINOPLE” OR “CONSTANTINOPLE IV.”
Now after the council, Ignatius was reinstated as Patriach. A few years later Ignatius died.
To cut long story short [and an interesting story it is] Photius was then installed as the Patriach. The legates reported this to the Pope. The legates were also sent to ask the emperor’s favor for Rome was in danger. Beside reporting about the new patriach, the legates also report that the emperor was sympathetic to Rome (eventually he sent his army).
The Pope hoped that by acknowledging Photius all will ends well. All censure against Photius was removed. Then on 879 Photius asked the Pope to send legates for another council, which he said will clear up matter.
THIS IS THE INFAMOUS COUNCIL OF CONSTANTINOPLE 879.
FROM THIS POINT THERE ARE TWO SIDE OF THE STORY BELIEVED BY CATHOLIC (Story A) AND ORTHODOX (Story B).
Story A:
In that council Photius repeated his all accusation against the Latin. Including the filioque. He also wanted Bulgaria back to Byzantine (there’s a long story about this, it’s enough simply to say that both Rome and Constantinople wanted Bulgaria).
The legates were pressured and bribed. They yield. Photius sent the act of this council to Rome. Pope John VIII re-excommunicated Photius.
Story B:
During the Constantinople Council of 879, “Photius was now all that any Pope could desire” He promised to repent and back off from Bulgaria. About the filioque, he diplomatically sidestepped it. The legates crowned him with a handsome vestment complimentary from the Pope.
Catholics accept Story A and thats the end of it.