Well, we have to do one or the other, but to be preoccupied with posture is to miss the point.
I areee with you that the disposition of the heart and mind is of primary importance in celebrating and receiving the Eucharist.
I simply don't understand why it has to be one or the other. Why can't it be both? Why can't the priest give the sacraments to the recipient in either position? This distraction, if you will, is from the "Pit of Hell" itself, and the devil has dangled it from his fishing pole in front of the Catholic Church, and the Catholic Church has taken that bait and swallowed it, hook, line , and sinker. The devil did this so that you will take your attention away from the reason Holy Communion is taken which is, "do to this (communion) in remembrance of me", to the ridiculous distraction of the "position to take when taking the sacrments. How foolish. It's tells God Almighty where our priorities lie, and reveals to Him that we are so very much "Babes in Christ, and cannot be fed the "meat" of the Word of God, because babies can only be fed "milk" How disappointing this must be to God, after 2000 years of existence on this Earth, we are arguing about "whether we should take communion standing up or kneeling" down. God help the Catholic Church!!!