ROFL. Been there, had many very similar conversations. Neither Dh or I wear our rings, haven't for years. Occasionally when we're out with friends the jewelry comparisons will start and someone will remark rudely on my bare hands. DH's standard reply is along the lines of
"I know we're married, wife knows we're married. we're really the only people who need to be concerned about honoring the vows we took. A ring may symbolize commitment but it doesn't make anyone to honor it. Not having rings on doesn't make us any less married or committed".
I go with "17 years, 3 kids, 2 dogs, a mortgage, car payment...trust me, we're plenty married!" or "No rings, our symbol is *high end piece of tech back at the house*".