Mr. Garth, 26, said that when he gets thanked it can feel self-serving for the thankers, suggesting that he did it for them, and that they somehow understand the sacrifice, night terrors, feelings of loss and bewilderment. Or don’t think about it at all.

“I pulled the trigger,” he said. “You didn’t. Don’t take that away from me.”

The issue has been percolating for a few years, elucidated memorably in “Billy Lynn’s Long Halftime Walk,” a 2012 National Book Award finalist about a group of soldiers being feted at halftime of a Dallas Cowboys game. The soldiers express dread over people rushing to offer thanks, pregnant with obligation and blood lust and “their voices throbbing like lovers.”…

The idea of giving thanks while not participating themselves is one of the core vet quibbles, said Mr. Freedman, the Green Beret. The joke has become so prevalent, he said, that servicemen and women sometimes walk up to one another pretending to be “misty-eyed” and mockingly say “Thanks for your service.”