210. He endowed these parents with abundant graces and blessings of his right hand, and enriched them with all virtues, with enlightenments of divine science and with the gifts of the Holy Ghost. After having announced to the two saints, Joachim and Anne, that He would grant them a Daughter, admirable and blessed among women, He permitted the work of the first Conception to take place, namely, that of the most pure body of Mary. The age of Anne, when She married Joachim, was twenty-four, and that of Joachim, forty-six. Twenty years they lived in married life without having an issue, and thus Anne, at the same time of the Conception of her Daughter, was forty-four years old, and saint Joachim sixty-six. Although the conception happened according to the ordinary course of nature, yet the Most High freed it from imperfections and disorders, permitting only what was strictly required according to nature, in order that the proper material might be furnished for the formation of the most perfect substance within the limits of a mere creature.

214. Much like to this, though much more wonderful, was the miracle of the Conception of Mary most holy in her mother Anne. The parents were so entirely governed by grace and withdrawn from concupiscence and delectation, that the accidental imperfections, which ordinarily are the material or the instruments of conception, and which induce original sin, were altogether wanting. Thus was furnished a material exempt from imperfection and furnished in such a manner that the act itself was meritorious. Hence in so far as this act was concerned it could easily be free from sin or imperfection, even if divine Providence had not previously arranged every particular of this event. This miracle the Almighty reserved solely for Her, who was to be a Mother worthy of Himself. For if it was proper that the material part of his being should have its origin according to the order maintained in the conception of the other children of Adam, it was likewise eminently proper that, without destroying nature, grace should concur in it with all its efficacy and power, and that it should excel in Her and act in Her more efficaciously than in all the children of Adam; yea, be greater than even in Adam and Eve, who gave origin to the corruption of nature and to its disorderly concupiscence.

This has been a fascinating topic.

I note that Eve is not even mentioned in the Catholic Encyclopedia entry on Original Sin.  The entry says Original Sin is the Sin of Adam and that Adam transmits death to his children.  I've always assumed that the Immaculate Conception was simply a truth transmitted through Tradition with no real explanation as to how it could be other than God's will that it be so.  But I now see that the dogma also has very logical roots in theological and even practical terms.  The fact that Original Sin is the sin of Adam and it is he who transmits that sin to all mankind through the centuries even to this day, then Blessed Mary couldn't be subject to Original Sin--in fact, it would be absurd to consider her subject to Original Sin--as she is not the product of Adam's conception.

It was explained to me here that the Blessed Virgin was begotten by her parents in holy obedience and complete purity of heart, and that thereafter they lived together in continence in the greatest devoutness and fear of God. I was at the same time clearly instructed how immeasurably the holiness of children was encouraged by the purity, chastity, and continence of their parents and by their resistance to all unclean temptations; and how continence after conception preserves the fruit of the womb from many sinful impulses. In general, I was given an overflowing abundance of knowledge about the roots of deformity and sin.

The parents were so entirely governed by grace and withdrawn from concupiscence and delectation, that the accidental imperfections, which ordinarily are the material or the instruments of conception, and which induce original sin, were altogether wanting. Thus was furnished a material exempt from imperfection and furnished in such a manner that the act itself was meritorious. Hence in so far as this act was concerned it could easily be free from sin or imperfection, even if divine Providence had not previously arranged every particular of this event.

This seems rather off.  It isn't concupiscence that transmits (induces) Original Sin, nor would lack of concupiscence prevent its transmission.

Accordingly the privation of original justice, whereby the will was made subject to God, is the formal element in original sin; while every other disorder of the soul's powers, is a kind of material element in respect of original sin.

I agree in general that the account of Adam and Eve given in Genesis doesn't quite add up, but I think that's just because it doesn't really tell us all the details of the story that would make it comprehensible in a fuller context. For example, it doesn't tell us all that much about why they ate the forbidden fruit, especially in Adam's case. He just says his wife gave it to him to eat, and he ate it. But it doesn't actually give us the reason why Adam ate it, or whether his excuse is accurate, which wasn't much of an excuse to begin with.

I'm not sure this follows.  Our Lady herself was still conceived of a man, even if her Son was not.