“He’s a classic politician,” said Steve Huffman, his partner in founding Reddit.

Like a good politician, Mr. Ohanian is happy to add to the speculation. “If I were to run, I’d run for representative, and I’d do it explicitly with the requirement that it’s only one term,” he said.

But for now, he is more interested in spreading good vibes in the tech world, particularly its East Coast wing. On a recent Wednesday, he arrived at his brunch spot near his Brooklyn Heights apartment, accompanied by his girlfriend of two years, Sabriya Stukes, a Ph.D. student in microbiology. They met in college, Ms. Stukes said, when she wandered into his dorm while he was playing video games.

“I asked him where my friend was,” Ms. Stukes said. “He said, ‘I don’t know,’ and then went back to playing video games.”

Mr. Ohanian, wearing a Nooka watch and (another) gingham shirt, said he moved to Brooklyn Heights because his father, who runs a small travel agency in Maryland, once dreamed of moving there. Repeating an oft-told tale, Mr. Ohanian said that the first thing he did after selling Reddit was to upgrade his father’s season tickets to Redskins games.

“The thing that I don’t usually tell,” he went on, “is that after that I called my mom and told her, ‘What do you want?’ Because this was a person who never wanted anything.” His voice caught in his throat. “And she said she wanted nothing.”

At the time, his mother was battling terminal brain cancer, having received a diagnosis in 2005, shortly after Reddit started. It had already been a tough year. A few months earlier, Mr. Ohanian’s girlfriend at the time attempted suicide by leaping out of a window in Germany. (She was in a coma for a while but recovered.) In September, his family dog was put down, and that same day his mother had a seizure, which led to the diagnosis.