Why the Mass in Latin?

[Melkite]

I see no reason to think that Photius lived a particularly holy life after he ended his rebellion against ecclesiastical authority.

I never said he lived a particularly holy life, I said he died in communion with Rome, reconciled to the Church.  As such, it is right to recognize him as a saint, since we know from Scripture that God rewards equally those who arrive at the 11th hour as he does those who arrive at the 1st, or, in Augustine's case, the 3rd or 4th.