Can the Congregation Join the Priest in Saying the "Through Him, With Him, In Him" Paragraph in the Liturgy?

It seems to be a common practice in Quebec for the congregation to recite the paragraph in the Liturgy beginning with “Through him, with him, and in him” along with the priest. At one church I went to, they also recited the paragraph or two leading up to the Sign of Peace. Changing the words to the Gloria and the Holy Holy also seem to be fairly common.

Which, if any, of these practices is permissible?

While its not on the level of the congregation saying the words of consecration, it is not the congregation’s part of the Mass. The Roman Missal clearly states that it is the celebrant’s (and concelebrants) role to say/chant the doxology.
For example, would you want to attend a play where characters say other characters lines?

As for changing the words of the Gloria or Sanctus, Liturgiam authenticam (emphasis added):

  1. A great part of the liturgical texts are composed with the intention of their being sung by the priest celebrant, the deacon, the cantor, the people, or the choir. For this reason, the texts should be translated in a manner that is suitable for being set to music. Still, in preparing the musical accompaniment, full account must be taken of the authority of the text itself. Whether it be a question of the texts of Sacred Scripture or of those taken from the Liturgy and already duly confirmed, paraphrases are not to be substituted with the intention of making them more easily set to music, nor may hymns considered generically equivalent be employed in their place.
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