The Augsburg Confession states that Lutherans have retained the Mass and the usual ceremonies, insofar as doing so does not compromise the Gospel. Here, then, we begin a step-by-step review of the Mass according to the Lutheran rite. Please note that the ad Orientem position is presupposed in all cases.
The historic rite begins the Mass with this rubric: "The priest, standing at the foot of the alter-steps, and signing himself with the sign of the holy Cross, begins...: In nomine Patris...."
A contemporary usage that has the celebrant facing the congregation and signing them (in the form of a blessing) is contrary to the historic understanding that the priest (and people) are hereby invoking the blessing of the Holy Trinity upon themselves and their participation in the Mass.
(I am curious as to the source and interpretation of this innovation in the Liturgy.)