When Mike Chambers was ready to sell his house in Boulder, Colo., last month, he interviewed a handful of real estate agents who promised he could fetch $2.75 million or more if he listed with them.

But the promise would come at a cost: Each agent wanted him to pay a commission of at least 5 percent, or $137,500.

Frustrated that not a single agent was willing to budge on the rate, Mr. Chambers, 39, decided to sell his house on his own, and he took to social media with the handle @realtorshateme to chronicle the process. His reels drew 50,000 views or more.

Within days, local agents were making their own social media posts that countered his points — an action that Mr. Chambers described as an aggressive campaign aimed at preventing him from making a sale on his own.

Call it the Realtor recoil.

One year after the National Association of Realtors agreed, as part of a legal settlement, to change a key rule on real estate commissions — a rule that had long upheld a tradition of commissions between 5 and 6 percent, little has changed.