It is not for us to judge a priest. We are only to obey the authority that God has placed over us.
Correct, which is to the Pope and the Bishops appointed over us.
Aquinas defined the Virtue of Obedience as the Virtue by which we conform our Wills to the Will of the one with authority.
In the matter of posture for the reception of Holy Communion, the Church has issued and approved rules. Thus it is the Church via the approved norms, that has the voice of authority.
Anything contrary does not carry authority, therefore their is no virtue practiced when one attempts to conform ones will to that which is contrary to the actual authority.
It is not a matter of judging the priest, but a simply recognition than there is no disobedience in choosing to either stand or kneel at one’s discretion.
So you are correct, we ARE to obey the authority to which God has placed over us, and a person who choose to either kneel or stand is obeying such authority
Unity with the parish should be desired
The Church does not see such unity of posture as being desired
For example, some bishops attempted to regulate the posture of those who had returned to the pew after receiving Holy Communion. Some chose to have everyone stand, others to have everyone kneel. They sought, as you did, to have a unity of posture
The Vatican ended up overruling such rules, and clarified what the Church desires in terms of unity of posture
The July 2003 Newsletter of the Bishops Committee on the Liturgy (BCL) noted the "controversy … over the proper posture of the faithful at Mass after receiving Holy Communion.
“In several dioceses people have been instructed that they must stand until the last person has received Communion, despite the long-standing custom that people knelt during the distribution of Communion”.
“Numerous inquiries” received by the BCL led Cardinal Francis George, chairman of the BCL, to submit a dubium (doubt, question) to the Holy See’s Congregation for Divine Worship and the Discipline of the Sacraments (CDW) on May 26, 2003:
Dubium: In many places, the faithful are accustomed to kneeling or sitting in personal prayer upon returning to their places after having individually received Holy Communion during Mass. Is it the intention of the Missale Romanum, editio typica tertia, to forbid this practice?
Cardinal Francis Arinze, Prefect of the CDW, responded to the question on June 5, 2003 (Prot. N. 855/03/L):
Responsum: Negative, et ad mensum [No, for this reason]. The mens [reasoning] is that the prescription of the Institutio Generalis Missalis Romani, no. 43, is intended, on the one hand, to ensure within broad limits a certain uniformity of posture within the congregation for the various parts of the celebration of Holy Mass, and on the other, to not regulate posture rigidly in such a way that those who wish to kneel or sit would no longer be free
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This directive was then published by Cardinal George to all bishops in the US, and the bishops who had rules contrary, that attempted to regulate posture in ways that the Church did not envision or desire, removed their rules.