**>> In eucharistic celebrations deacons and non-ordained members of the faithful may not pronounce prayers e.g. especially the eucharistic prayer, with its concluding doxology or any other parts of the liturgy reserved to the celebrant priest. Neither may deacons or non-ordained members of the faithful use gestures or actions which are proper to the same priest celebrant.<< **
But the over-riding factor here is that we are to assist at Mass in a pious and reverent fashion. (We aren't imitating the priest, we are merely folding our hands in prayer.)
[This page contains the Table of Contents of the GIRM, which links into the text at the United States Conference of Catholic Bishops site.]
See also the 2003 GIRM in PDF format.
for the Dioceses of the United States of America
The General Instruction of the Roman Missal
The Structure of the Mass, Its Elements and Its Parts