A Surprise Guest at the S.E.C.’s Annual Gathering

WASHINGTON â€" In a room overflowing with suited lawyers scribbling handwritten notes, the man live tweeting in a hooded sweatshirt stood out.

Mark Cuban, the billionaire entrepreneur with a sartorial style best described as weekend wear, made a surprise appearance on Friday at the Securities and Exchange Commission’s annual conference in Washington. Wearing jeans and a gray hoodie, Mr. Cuban was easy to spot toward the back of the room, a seated observer chronicling the event on Twitter.

While the conference is typically a love fest for the agency â€" an opportunity to reflect on the past year’s triumphs â€" Mr. Cuban’s presence was a reminder of a setback. In October, the S.E.C. lost an insider trading case against Mr. Cuban, who used his victory as a platform to attack the agency’s broader approach to policing the markets.

But Mr. Cuban, who has announced plans to publish S.E.C. trial transcripts on his blog to highlight what he sees as the agency’s problems, was on his best behavior when talking to a swarm of journalists on Friday.

“There’s no hate for the S.E.C.,” Mr. Cuban, the owner of the Dallas Mavericks basketball team, told reporters during a brief break from the conference, known as S.E.C. Speaks. “No animosity.”

Instead, Mr. Cuban said he was there “to learn” about the S.E.C. and its mission.

The conference, run by the Practising Law Institute, featured speeches from top officials, including Mary Jo White, the agency’s chairwoman.

“It’s been a great conference,” he declared, carrying a package of legalistic literature circulated at the event.

You might think Mr. Cuban would be persona non grata at an S.E.C. junket. Yet a small crowd lined up to snap pictures with the billionaire, who sheepishly obliged the fans’ requests.

Was this an olive branch to a longtime nemesis? Well, let’s not get carried away. But coming from a man who fancies himself a watchdog of wrongdoing â€" whether it is an unjust S.E.C. case or a basketball referee’s blown call â€" the remarks were measured.

And at the very least, he took a softer stance from his prior statement that he hoped his insider trading acquittal would “shine a light on the S.E.C. abuses that I have witnessed.”

Even so, Mr. Cuban managed to lob a few jabs at the agency. “At no point do they say, ‘We made mistakes,’ ” he said.

He also vented his frustrations on Twitter, posting a series of real-time musings.

“There is a shocking lack of self awareness at the SEC,” one message read. “Nothing is their fault.”

When it came to a speech from Luis A. Aguilar, a Democratic commissioner at the agency, Mr. Cuban found plenty to like.

“Commissioner Aguilar â€" no institutional memory at the SEC … amen,” he wrote.

And when Mr. Aguilar critiqued the “significant turnover” at the agency, Mr. Cuban chimed in once again.

“Love the fact that Commissioner Aguilar is CRUSHING the S.E.C. on its turnover. # I’m liking this guy a lot.”