Lest anyone believe that the Orthodox Church holds to the doctrine of purgatory on account of the Confession of Dositheus, you should know that that particular document was written to contest the heretical writings of an Ecumenical Patriarch who had embraced Calvinism. It is a pretty good exposition of Orthodox belief but hardly exhaustive nor 100% accurate, Decree 18 in particular having been universally rejected.
The Church of Constantinople rejects completely the notion of purgatory. It is a matter of faith that no soul can, by any action after death including suffering, affect its eternal destiny. We spend eternity with God after the Last Judgment not because we in any way are worthy of that but rather because of God’s mercy.
“The Orthodox Church does not believe in purgatory (a place of purging), that is, the inter-mediate state after death in which the souls of the saved (those who have not received temporal punishment for their sins) are purified of all taint preparatory to entering into Heaven, where every soul is perfect and fit to see God. Also, the Orthodox Church does not believe in indulgences as remissions from purgatoral punishment. Both purgatory and indulgences are inter-corrolated theories, unwitnessed in the Bible or in the Ancient Church, and when they were enforced and applied they brought about evil practices at the expense of the prevailing Truths of the Church. If Almighty God in His merciful loving-kindness changes the dreadful situation of the sinner, it is unknown to the Church of Christ. The Church lived for fifteen hundred years without such a theory.”
Indeed, the Orthodox Church does not and never has taught anything resembling the Purgatory, and for a good reason. The Orthodox Church does teach that memorial services for the departed ease, through love, the discomfort (of shame) of those (most, all) who died without having confessed and repented of all their sins.
Regardless of whether they have or have not, some are believed saved immediately after death by God's mercy alone, their sins having been forgiven for reasons known only to God. This immediate or Particular Judgment is the announcement of what their final state will be following the Final Judgment when Christ returns.
In the interim period between the physical death and the Particular Judgment immediately following it, and the resurrection and the Final Judgment, there is no "purification," there is no repentance after death believed possible. Those souls that are believed saved at the end of their physical life by the Particular Judgment immediately following the physical death are saved entirely by the means of God's grace, the way their sins are remitted by God during their life on earth through confession and repentance and not through some torturous means.
The Orthodox do believe that, when their sins are made visible to all the souls experience various degrees of shame and discomfort from it since everyone sees what they have said an done and thought. The discomfort is also believed to come the knowledge that despite their sins and lack of repentance, they have been saved through god's grace, as they realize how undeserving of mercy they are and yet have been spared by the love of God and nothing else.
So, Orthodox memorials are not petitions to "purify" the soul but expressions of gratitude to God for having saved their loved ones; they are acts of love (spiritual hugs if you wish) that are believed to ease the discomfort of shame the departed experience spiritually in their humiliation.
The Catholic dogma of Purgatory, as can be seen in the article, invoked the temporal fires that somehow "roast" the sinful soul to God's "satisfaction" and is in a way a grotesque distortion of what the Church in the East always believed about the souls of the departed.
As with everything else Catholic, much of the dogma has been attenuated after the Vatican II, eliminating the temporal fires and "roasting" in an attempt to re-invent the wheel. Nevertheless, the idea that the souls are undergoing some purification, change, what not, remains. Likewise, the idea that indulgences somehow help speed up or aide this purification process (now that's a strange concept in God's realm) are equally alien to the East. The good thing was that the Protestants recognized these distortions but then, rather than turning East, only intensified the flawed Augustinian dead-end teachings.
By the way, the attempt of the article to cite early evidence of Christian belief in Purgatory is at best naïve. The early evidence simply expressed the Christian belief that God saved them by his mercy.