At last, Twitter is listening. Or it is now that "the rest of the world knows."

An internal memo from Twitter's CEO of the past five years, Dick Costolo, was published by the Verge this week. As Slate noted, it "cleared up one of the abiding mysteries of the Internet: Do the people at Twitter know how serious their trolling problem really is? The answer turns out to be yes."

In the memo, sent to staff Monday, Costolo at first sounds humble and frank, admitting the company sucks "at dealing with abuse and trolls on the platform and we've sucked at it for years." He says he's ashamed and takes full responsibility. In a follow-up message sent Tuesday, he takes taking full responsibility.

The notes were sent, according to the Verge, in response to an internal-forum note from an employee asking whether anything could be done to address recent stories on This American Life and in the Guardian about Lindy West, a feminist writer who confronted a particularly noxious online tormentor and who called out Twitter for tolerating such extraordinarily abusive behavior. Such stories are particularly plangent to the many women who have been victims of Twitter-related abuse or harassment of any kind--though they come after years and years of complaints, articles, investigations, and explorations of widespread harassment and bullying on Twitter. Apparently, it took this particular media spotlight on the issue to force the company's hand.  

And, as Costolo now acknowledges, "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."

So. The scales have tipped to the point where losing users and public opinion finally costs more than maintaining a free-speech-above-all stance that the company has stubbornly maintained for, well, basically its entire existence. ("We're the free speech wing of the free speech party," Costolo told a San Francisco audience in 2011.)

Note that Costolo does not apologize to West, nor to any other victims of the rampant harassment on Twitter. Nor does he point out that banning trolls and responding responsibly to harassment complaints is simply the right thing to do.

That's a shame. It's also a shame that Costolo attempts to take all the blame himself for this longstanding behavior. It's actually both a cultural issue for the company, to say nothing of a routine customer-service matter, which means it is the responsibility of a huge department of people at this prominent publicly traded company.

As someone who has taken the time to file harassment complaints to Twitter (a fairly arduous and often frustrating process) only to have them explicitly and specifically denied, via email, I know how receiving such denials stings. And it feels personal. Someone at Twitter actually looked at the tweets in question, and considered and... shrugged.

But that's not an isolated shrug. It's a systemic shrug. And that is Twitter's problem.