An excerpt from the distribution of holy communion during today’s worship service:
Me: The Body of Christ, given for you.
Member: Thank you.
Thank you. What a great response to receiving the great gift of holy communion. In the piety that I learned from my mother and at my childhood congregations, the "appropriate" response to receiving the sacrament was always a firm "Amen." Yet at St John’s by the Gas Station, my internship congregation, I hear many respond with "Thank you" or even "Thanks," a few with "Thanks be to God," and some with the "Amen" to which I am accustomed.
I presume that many of the folks who say "Thank you" were not raised in the same fashion I was raised. Perhaps they were not raised in a liturgical church, or at least not one with a piety that requires a firm "amen" upon receiving the sacrament. Their (perhaps untrained) response of "thank you" speaks to a genuine response of gratitude to receiving a gift, not a learned liturgical refrain prompted by a hymnbook’s rubric.
A piety of gratitude, perhaps, expressed in the ordinary language of our daily lives?
Thank you.
The Lutheran Zephyr 
I’ve served communion a few times and I’ve never heard a verbal response, nor have I ever heard one from my fellow communers.
But the eyes…serving communion, looking into the eyes of the people…that speaks volumes.
I’m not sure that looking into the eyes is easily done when we kneel, but once/month we do walk through communion and the eyes can easily meet.
I once communed a woman whose response was, “It certainly is!” I loved it.
There is a homeless guy who occasionally worships with us. He very obviously has some addiction/mental health issues.
Most of the time, the people in the congregation are fairly welcoming, and will even give him food if it is a food bank week or a few dollars if it isn’t, but there are a few ushers who won’t let him into the sanctuary because he “isn’t dressed appropriately.” They will let him participate from the narthex, though.
This week was one of those weeks, and the usher in question apparently asked him to leave right after communion. Before he left the church, he yelled loudly, “Thank you, Father!” speaking to the pastor (he obviously also has Roman Catholicism in his background from his actions during worship). Some of the old folks in the congregation gave him dirty looks, but I thought it was kind of neat.