31. Likewise it is also for the Priest, in the exercise of his office of presiding over the gathered assembly, to offer certain explanations that are foreseen in the rite itself. Where this is laid down by the rubrics, the celebrant is permitted to adapt them somewhat so that they correspond to the capacity for understanding of those participating. However, the Priest should always take care to keep to the sense of the explanatory text given in the Missal and to express it in just a few words. It is also for the presiding Priest to regulate the Word of God and to impart the final blessing. He is permitted, furthermore, in a very few words, to give the faithful an introduction to the Mass of the day (after the initial Greeting and before the Penitential Act), to the Liturgy of the Word (before the readings), and to the Eucharistic Prayer (before the Preface), though never during the Eucharistic Prayer itself; he may also make concluding comments regarding the entire sacred action before the Dismissal.
Commentators, thankfully, have largely disappeared like the dinosaur. Or at least gone the way of the coelecanth. But GIRM 31 has some good advice:
- - few words
- - very few words
- - comments are optional
Note that comments are “never” permitted during the Eucharistic Prayer.
Do you still get occasional requests for a “teaching Mass?” One in which the priest or someone offers a running commentary as the worship progresses? We still do at the student center, and I’m curious if this is just a scattered phenomenon.