I don't understand where the Communion of Saints fits into this.
I thought in the Catholic tradition the Community of Saints represents Church Militant praying for the dead.
I am not sure, but I think the Church settled this matter in the 8th century. The menaing of this Community involved the Siants who are in heaven (i.e. those who have achieved theolsis, or likeness of Christ; that is real saints, not the "holies" who share in faith and sacraments on earth; I think the Protestants refer to themselves as saints or the divines -- Calvinists and lutherans respectively). If you wonder if the souls can pray, the Church certainly says they can pray, but they can't repent. Our time for repentance is on earth. When we die, our souls are immediately subjected ot judgment.
"And as it is appointed unto men once to die, and after this the judgment" (Heb 9:27)
Once judged, what good is it for us to repent; the judgment is passed.