Is a simple bow of the head acceptable reverence for the REAL Presence of God in the Tabernacle or when He is exposed on the Altar? No, it is not.
Genuflection is the only gesture worthy enough for the real presence of God. This would include the tabernacle - at all times that anyone passes in front of it . A genuflection to the altar is necessary only when the consecrated host is present on the altar OR if the tabernacle were also on the altar. A profound bow is proper to the altar when it does not have the REAL PRESENCE sitting upon it (in any form). You would profoundly bow to the place of the sacrifice, the altar when empty, in acknowledgement of its status as the altar of sacrifice of the REAL Body Blood, Soul and Divinity of Jesus, GOD the Son (offered to the Father in Mass).
234. There are two kinds of bow, a bow of the head and a bow of the body:
a. A bow of the head is made when the three divine Persons are named together and at the name of Jesus, Mary and the saint in whose honor Mass is celebrated.
b. A bow of the body, or profound bow, is made: toward the altar if there is no tabernacle with the blessed sacrament; during the prayers, and within the profession of faith at the words, <by the power of the Holy Spirit>; in Eucharistic Prayer I (Roman Canon) at the words, <Almighty God, we pray>.
Isn't our show of reverence our personal preference?
The GIRM (The General Instructions of the Roman Missal) must be followed exactly, without modification by individuals or clergy.
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Canon 846 says: “The liturgical books approved by the competent authority are to
be faithfully observed in the celebration of the sacraments; therefore, no one on personal authority may add, remove, or change anything in them.”
From GIRM (The General Instruction of the Roman Missal)
IV. Some General Norms for All Forms of Mass
Veneration of the Altar and the Book of the Gospels 273. According to traditional practice, the altar and the Book of the Gospels are venerated by means of a kiss. Where, however, a sign of this kind is not in harmony with the traditions or the culture of some region, it is for the Conference of Bishops to establish some other sign in its place, with the consent of the Apostolic See.Genuflections and Bows274.
A genuflection, made by bending the right knee to the ground, signifies adoration, and therefore it is reserved for the Most Blessed Sacrament, as well as for the Holy Cross from the solemn adoration during the liturgical celebration on Good Friday until the beginning of the Easter Vigil.During Mass, three genuflections are made by the priest celebrant: namely, after the showing of the host, after the showing of the chalice, and before Communion. Certain specific features to be observed in a concelebrated Mass are noted in their proper place (cf. above, nos. 210-251).
If, however, the tabernacle with the Most Blessed Sacrament is present in the sanctuary, the priest, the deacon, and the other ministers genuflect when they approach the altar and when they depart from it, but not during the celebration of Mass itself.
Otherwise all who pass before the Most Blessed Sacrament genuflect, unless they are moving in procession.
Ministers carrying the processional cross or candles bow their heads instead of genuflecting.275. A bow signifies reverence and honor shown to the persons themselves or to the signs that represent them. There are two kinds of bows: a bow of the head and a bow of the body.
A bow of the head is made when the three Divine Persons are named together and at the names of Jesus, of the Blessed Virgin Mary, and of the Saint in whose honor Mass is being celebrated.
A bow of the body, that is to say a profound bow, is made to the altar; during the prayers Munda cor meum (Almighty God, cleanse my heart) and In spiritu humilitatis (Lord God, we ask you to receive); in the Creed at the words Et incarnatus est (by the power of the Holy Spirit . . . made man); in the Roman Canon at the words Supplices te rogamus (Almighty God, we pray that your angel). The same kind of bow is made by the deacon when he asks for a blessing before the proclamation of the Gospel. In addition, the priest bows slightly as he speaks the words of the Lord at the consecration.
