My favorite MR3 response:
And also with your spirit.
No really. I’ve said that more than the old and the new combined.
My wife reports she got a dirty look (?!) for uttering “and also with you” out of step from most of the rest of the assembly.
I was reading on a blog or two about how disappointed one or two commenters are that Father isn’t stepping in to correct “wrong” responses when they happen. Personally, I’d investigate putting electric buzzers in the pews. That’d shock those pew potatoes into MR3, by gum.
All kidding aside, how would you handle “wrong” responses from the purple chair of authority? Screw ars celebrandi and be stern at every opportunity? Trust your preparation and pew cards will eventually be enough? Three strikes and then give ’em hell on Advent IV? Hope the problem goes away? Do tell.