He shakes his head and fidgets in his seat during testimony, passes notes to his lawyers and blows kisses to his mother in the courtroom gallery. Sometimes Sean Combs pulls out chairs for the women on his legal team.

His federal trial has drawn worldwide attention, with minute-by-minute coverage from the press and social media influencers who broadcast live updates from the street outside U.S. District Court in Lower Manhattan.

But since federal courts bar cameras, Mr. Combs’s demeanor during the most critical eight weeks of his life — Does he smile? Does he seem mad, nervous, sad? — has been largely outside public view, captured only by the sketches of courtroom artists.

For weeks now, Mr. Combs, who is facing sex-trafficking and racketeering conspiracy charges that could put him in prison for the rest of his life, has been an attentive and largely easygoing presence in the courtroom. His expressions of disagreement with witnesses have been subdued, showing no inkling of the volcanic, violent temper often described in testimony.

When George Kaplan, a former assistant, described the pace of working for Mr. Combs as “almost like drinking from a fire hose,” the mogul nodded in approval. When another assistant, using the pseudonym Mia, said she would be punished if she did not do “everything that he told me to do,” he just scoffed and shook his head.

It is an understated posture for a man whose profile as a chart-topping producer, rapper, reality-TV star and gossip-page fixture was larger than life, giving rise to the multitude of nicknames — Puff Daddy, Diddy and Love — by which he has been known.