In a keynote event at the Great Place to Work annual conference in Dallas, Texas, the conversation focused on the importance of transparency in the work place and Costolo’s tips for open communication among CEOs and employees. Twitter (TWTR) debuted at No. 24 on the Best Places to Work list this year.

Early in the conversation, Fortune questioned Costolo about a controversial response he shot off to employees in February on an internal forum which charged that Twitter “sucks” dealing with harassment on the social media platform, joked about the email at the conversation’s start. “I never use that kind of coarse language in an email.” The memo read:

We suck at dealing with abuse and trolls on the platform and we’ve sucked at it for years. It’s no secret and the rest of the world talks about it every day. We lose core user after core user by not addressing simple trolling issues that they face every day.

I’m frankly ashamed of how poorly we’ve dealt with this issue during my tenure as CEO. It’s absurd. There’s no excuse for it. I take full responsibility for not being more aggressive on this front. It’s nobody else’s fault but mine, and it’s embarrassing.

Costolo said his mother saw the leaked memo and chided him, “Don’t you have a better vocabulary than that?” he added, however, that the email ensured he took responsibility for the harassment issues and that he shouldered the effort to enact change at Twitter. Since then, the platform has added privacy options and two-step authentication features to cut down on account piracy.

Costolo went on to discuss the importance of transparency in light of the company going public in November 2013.

“It’s a particular challenge for companies going public to think of how they can maintain open lines of communication and share as much as possible,” he said. “There’s a tendency among functioning organizations, a natural tendency, that we shouldn’t share that information.”

Costolo, who joined Twitter in 2010, has seen the company triple in size during his tenure to over 3,600 employees globally. CEOs and executives tend to use going public as “an excuse,” he said. “It’s better to give more information, to tell more about metrics and not hide behind [them]. It’s critical for the leader of an organization to fight against that and be very vocal about pushing against that.”

Costolo said that scaling communication as a company grows is key for success.

“You have to design it into the company and architect it,” he said. It’s important to then be able to measure communication against strategy. As part of that, he said he makes sure to speak with all new hire classes. “I take time out personally to go talk to them. I spend most of that time answering questions,” he added.

Discourse and debate among employees are paramount to success, too, and fostering a great place to work: “Anyone in the company can ask me anything. I like it when people do. I like it when people challenge me. They start to understand that anyone in the company can have a question or debate. I encourage that from day one in the new hire orientation session,” Costolo explained.
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That type of conversation leads to transparency and increased communication, enabling a more efficient workplace.

“The most important thing in a learning organization is to get to the truth. The fastest way to get to the truth is discourse,” he said. “The challenge there, the really, really hard part, is when you start to have debates.” But there are certain debates that are productive and those that aren’t, he explained. “Discourse isn’t about interrogating and being a prosecutor. It’s about open debate to get to the truth.”

Part of that, too, is ensuring managers are open to communicating with their teams effectively. To help, Costolo teaches management courses to everyone working with a large group of people in the company. “It’s your job to improve your team,” he said in the way of advice for managers at Twitter and elsewhere.

Costolo was asked at the conversation’s end about the best advice he ever received. He pointed to what Ben Horowitz, the partner at the venture capital firm Andreessen Horowitz, once told him. “Make sure everybody understands what you understand,” said Costolo. “You may think you’ve helped explained and given context 91 times and you still have people who don’t understand why you did x.” As a result, it’s important to give and explain “the context for decisions that have been made.” That way, he added, the workers will “commit to executing” that mission.
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(Correction: An earlier version of this story incorrectly identified the number of Twitter employees globally. It is 3,600.)