I know that on Christmas and the Feast of the Annunciation in the Ordinary Form we are required to kneel during the words, “For us men and for our salvation he came down from heaven, and by the Holy Spirit was incarnate of the Virgin Mary, and became man.” and I know the normal practice for the rest of the year is to bow, but are we allowed to genuflect?
I don’t see a prohibition against genuflecting at those words.
This will, of course, revive the debate between those who say that something like this would be illicitly “adding” something to the Mass which is not there in the rubrics, and those who find it foolish that, unlike previous Missals, those who cobbled up the Novus Ordo were/are obsessed with what the laity is doing during Mass.
Motive should be examined, as well. Do you want to genuflect in order to draw attention to yourself? Are your motives pure?
If this were a question coming from an individual, might respond “Yes, you may genuflect at that phrase, but don’t draw a lot attention to yourself, and don’t sneer at others who are following rubrics and with a bow.”
If this were from a group in the parish (e.g., Holy Name Society, Fraternal Knights of the Incarnation, etc.) who wanted to start doing this, I would enthusiastically support it as the development of a legitimate custom.
I think this is one of those things that should be brought back into use, one way or another.