Mr. Karp, who founded the blogging service Tumblr, talked in depth about why his service did not provide a mechanism for commenting on Tumblr sites. He said the absence of such a mechanism was intentional, to prevent nasty comments. He said comments on most sites mad people feel like second-class citizens. “It makes you feel like you have to speak in all caps,” Mr. Karp said.

He said that no one had really figured out how to conduct meaningful and pleasant conversations online, but that he wanted to try to solve that difficult problem.