What this person was referring to was my genuflection during the creed. This life-long Lutheran had never seen it before and had assumed that I was merely an old man having a bad day (which could have been correct and was a fairly logical assumption). But that was not it. I was genuflecting during the creed, specifically at the words,
[Who for us men and for our salvation, came down from heaven, and] was incarnate by the Holy Spirit of the virgin Mary and was made man... (Et incarnátus est de Spíritu Sancto ex María Virgine et homo factus est...)
These words are sort the fulcrum of the creed. Everything we confess about God hangs on these words. The genuflection at these words (or a deep bow for those of the Novus Ordo crowd) has been around for more than a thousand years. We are not exactly when it began or where but we know by 1150 AD that it was common practice (if not universal). Peter of Cluny (d 1156) tells us that genuflection at the words et homo factus est was a custom everywhere. Some certainly had it earlier and some perhaps later but he writes as if it were the norm.
Here is an example of the faithful evolution of liturgical practice. The Church has always held that the incarnation of our Lord is not only the core of our proclamation but that God condescending to become flesh and blood is rightfully met by the humility of faith that not only acknowledges Him as God of God, Light of Light, and true God of true God, but receives Him with faith. The outward expression of this faith is the gesture of honor, the genuflection or kneeling at the words which confess this central truth and the lynch pin of our faith and confession. God became man.
You can put Scripture to this. Recall how St. Paul says that at the name of Jesus every knee shall bow and every tongue proclaim Him Lord. But there is not particular passage to mandate such liturgical gesture. Merely the response of faith.
To be sure, the practice is still not uniform. Some Lutherans disagree about where to genuflect or if to genuflect at all (check out this or that). Luther highly esteemed the custom and praised it in his commentary on St John’s Gospel (LW 22:102, 105) and mentions it again elsewhere in positive terms.
What of genuflection? Genuflection (or genuflexion), bending at least one knee to the ground, was from early times a gesture of deep respect for a superior. In 328 BC, Alexander the Great introduced into his court etiquette some form of genuflection already in use in Persia. In the Byzantine Empire even senators were required to genuflect to the emperor. In medieval Europe, one demonstrated respect for a king or noble by going down on one knee. We know it most commonly today during a proposal of marriage. (borrowed from Wiki)
Well, if Alexander the Great or Byzantine senators or European royals thought it was honorable to genuflect or kneel as a sign of humility, I think that we can see why this became the practice of the Church. And to those who eschew practices as too "Catholic," I would ask why your intended deserves more in marriage proposal than does our Lord at the confession of His incarnation?
For those who find this utterly confusing, I cannot but help to pass on (in good humor) a cheat sheet prepared for those who find liturgical posture and gestures impossible to decipher. In the end I can think of no better way than to quote Pr Will Weedon from a few years ago:
Now, I was challenged on this and it was pointed out that I do not observe these rites as they are printed. The point being that I elevate, I genuflect, I sign myself with the cross on forehead, lips and heart before the Gospel, I kiss the Gospel book and the altar, and so on. In short, I do ceremonies that are neither prescribed nor suggested.
I would respond, though, that there is a great difference between adding ceremonies (especially historic ones) and dropping ceremonies or parts of the rite which are explicitly prescribed. Certainly in the rubrics of all three books, there are ceremonies that are suggested but not prescribed ("may" rubrics). The worth of any ceremony is in what it confesses. And above all, I'd argue, the text and the ordering of the text in each rite should be respected precisely as it stands.