When I say commentary I mean ancient commentary, or you could call it supplemental texts, ancient homilies, whatever. I mean writings closer to the actual time of Jesus. People like Ambrose, Jerome, Augustine of Hippo, Gregory Nazianzus, Basil of Caesarea, John Chrysostom, Irenaeus of Lyon, Clement of Rome, Ignatius of Antioch, Justin Martyr, Clement of Alexandria, even Origin or Tertullian, and so on...
Protestants basically ignore that there's a TON of writings from the early church.
Even slightly later writings like John Climacus are still much, much closer to the time of Jesus and the early church than the reformation is, nevermind modern times.
One Protestant ministry I find helpful equips protestants to understand the Christian gospel and contemporary paganism by drawing on the rich heritage of Irenaeus's apologetic defense against the pagans of his day. That particular ministries entire idea was seeing the connection between global paganism and gnostic belief in the first centuries of the church, realizing that Irenaeus had already done the heavy theological lifting, and the current need was to learn from him (and other church fathers) and recontextualize their insights for the church today.
For many protestants I've known, the church fathers and the ecumenical councils are seen as helpful, but never carrying the same authority as the Scriptures. The authority of councils and creeds is derived from the Bible, not the inverse.
In a couple of places, Jaroslav Pelikan quotes Benjamin Breckenridge Warfield's Augustine and Calvin (a book and an author I've never heard of elsewhere) as saying "the Reformation, inwardly considered, was just the ultimate triumph of Augustine's doctrine of grace over Augustine's doctrine of the church." A selection of Luther's writings shows numerous entries for Augustine in the index--not all for support, it is true.
A dip into Calvin's Institutes of Religion turns up references to Ambrose, Augustine, Jerome, Gregory Nazianzus, Basil, Chrysostom, and Bernard of Clairvaux.
Protestants basically ignore that there's a TON of writings from the early church.
Even slightly later writings like John Climacus are still much, much closer to the time of Jesus and the early church than the reformation is, nevermind modern times.