"The feature, which lets people republish another persons' post on their own Tumblr blog, came about in 2007 as the company tried to come up with a new way for people to give feedback without "the world of horrible anonymous Internet awfulness," said Tumblr CEO David Karp at the GigaOm RoadMapconference Monday in San Francisco. Tumblr, which has 160 million users, was designed as a platform for creative people, so comments had to focus on them, Karp said.
With reblogging, if people want to criticize another post on Tumblr, they have to also publish the post on their own blog. The hope was that this would cut down on nasty comments. The reblog was also designed to give interactions on the blog more focus instead of just being text comments in small fonts.
"We racked our brains figuring out what to do instead of commenting," Karp said. "We realized we needed some mechanism for feedback... To say something you had to have your own soapbox over here and take what I say and you wrap your commentary around it. You're not allowed to just show up and say I'm a jerk. It's much harder to twist my words."
(David Karp: Tumblr Reblogs Created To Fix Comment 'Awfulness'. (2012). Forbes.com. Retrieved 27 July 2019)