From a priest:
I was concelebrating a Mass last week (N.O., in English) and the principal celebrant substituted the word ‘all’ for ‘many’ at the consecration. I gather he does this at every Mass he offers. Does that change render the Mass invalid and/or illicit?
See how annoying concelebration can be? Concelebration should be safe, legal and rare.
Ad rem: No, his illicit and abusive changing of the words of consecration did not in this case invalidate the consecration. Furthermore, it was a concelebration.
However, if the priest does this all the time, his pastor (if he is an assistant) and the local bishop should be informed. It could be useful to send a copy to the Congregation for Divine Worship.
The issue of pro multis was and still is very controversial. If a priest were during the Gloria to make a substitution and say “Glory to God in the highest, and on earth peace to MEN of good will” instead of the dopey choice made by ICEL and the Holy See for “on earth peace to PEOPLE of good will”, that would be wrong, but it wouldn’t be as bad as changing the words of consecration. BTW… my objection to “people of good will” is that the two-syllable word destroys the flow of the sentence. They really needed a one syllable word, but I digress.
Priests are bound to stick to the texts in the books.
However, it is still possible that, even after a few months, a priest will slip and use the obsolete ICEL texts from memory. We shouldn’t be worried about a slip here and there. But if a priest is regularly changing the words of consecration – especially after all the controversy over that very point – he has stepped over the line. He must stop what he is doing or be stopped by proper authority.
Finally, may I suggest that you send Father a gift of one of my Say The Black Do The Red “New Translation” edition coffee mugs? Maybe he needs a reminder that there is now a new translation. Perhaps with some Mystic Monk Coffee?