The J. Mendel dress is no longer available, but Bergdorf’s sold it this year. Reportedly it cost about $6,000, which is pricey, but on the scale of expensive dresses, not so much (the Chanel frock, which was couture, probably cost about four times that, at least).

It was chosen because the shade went well with the rose garden, as well as the night’s décor, which was green and gold to reflect the state colors of Australia. No deeper reason.

While her office fulsomely described the reasoning behind the flowers and the meal (“The menu for the State Dinner with Australia highlights the lush, late summer season across the vast lands of America. The menu pays homage to Australia’s special blend of culinary adaptations from its various cultures, not unlike the diverse food traditions of the United States”), when it came to the dress, it simply offered the designer and a description.

“Melania Trump Makes Waves,” read the headline in USA Today. But she didn’t. Not at all. Maybe she decided to leave all that roiling of the waters to her husband.

And maybe that should be enough. Maybe the fact that the first lady shows up, does her job with decorum, and looks impeccable, is all we should ask from this particular nonelected position. Her husband wore his usual tux, jacket flapping open. Mr. Morrison buttoned his. Mrs. Morrison wore two looks from the Australian designer Carla Zampatti: a black dress on arrival and a halter-necked sequined navy column with a silk scarf to the dinner.

And yet there’s something dispiriting about the idea that at one of the grandest public occasions orchestrated by the White House, and managed largely by the East Wing — one full of pomp and circumstance and staging — the costume of the leading lady should be hailed as successful because … it’s pretty.