I have been to a few masses that do this. Sometime after the procession but before the penitential rite, everyone greets each other much like we do when we show each other a sign of peace. Turning to our neighbors, shaking hands, hugging, etc.
To me, this is totally out of sync with the somber reflection we need to have in order to prepare ourselves for the penitential rite and Mass. For me, it goes like this…kneel, praying for weekly shortcomings, mass intentions…switch modes to be chipper and friendly, then quickly get back into prayer/refelction mode to prepare for penitential rite…just does not flow for me at all! Anyone?