Telling anyone about My Diner, a Southie landmark that has maintained its authentic retro appearance as the waves of gentrification have begun to swell, is bound to trigger a round of Abbott and Costello–like jousting. But with a colossal menu that covers all the old-fashioned comfort-food bases — from French toast ($3.75-$5.25) and piled-high club sandwiches ($5.75–$6.50) to salads ($3.95–$6.95) and a roast-beef dinner with mashed potatoes and a veggie ($8.95) — the cozy spot is egalitarian enough that you can comfortably call it your own, no matter where your preferences lie. Health nuts, don’t be daunted by the greasy-spoon image and the sounds of the fryer. Rest assured that the turkey is vertically roasted, a cooking method that keeps the natural juices in and allows fat to drip out. It can be had hot with stuffing and cranberry sauce ($6.95–$8.95) or in a sandwich ($4.95). And if there are 10 commandments of dining out, not far behind “Thou shalt not eat sushi on Mondays” is “Thou shalt eat an omelet in any place where black-and-white-checkered tiles decorate the wall.” Case in point: the omelets at My Diner — including spinach, tomato, and feta ($6.25) and turkey and cheese ($6.25) — are as big as a small hubcap and as pillowy as a down jacket.

In true retro fashion, regulars here offer unsolicited tips. On a recent Friday afternoon, I took a seat beside Frank, who’s allegedly as much a fixture at the counter as the chrome-and-neon-ringed clock on the wall. The waitress added one cream to his ceramic coffee mug. He thanked her, then noticed I was slow in ordering.

“Don’t worry,” he said. “Whatever you get here, it’s very good.” Sounds like my kind of place.

My Diner, located at 147 98 A Street, in South Boston, is open Monday through Saturday, from 5 am to 3 pm, and on Sunday, from 6 am to 2 pm. Call 617.268.9889.