Julie Ann Horvath, an influential engineer at GitHub who has been vocal about the company’s increasingly positive culture for women, has left the open-source code platform and is alleging on Twitter that there was gender-based “harassment” targeted at her there.

You can see several of her tweets here that began last night:

https://twitter.com/nrrrdcore/status/444646763299753984

https://twitter.com/nrrrdcore/status/444647167118958592

https://twitter.com/nrrrdcore/status/444650888859099136

https://twitter.com/nrrrdcore/status/444653632919584768

https://twitter.com/nrrrdcore/status/444881005011140608

Horvath, who joined San Francisco-based GitHub in 2012, also founded its laudable Passion Projects series of women in tech talks to “surface and celebrate the work of incredible women in our industry, as well as produce more female role models within the tech community.”

Nonetheless, GitHub has been embroiled in a series of diversity controversies, such as programmers adding racial and sexist slurs into their code. But with Passion Projects and hires like Horvath, GitHub CEO Tom Preston-Werner said he was trying to change that culture.

The talks encouraged more women to join the company, and he said a quarter of the 60 new hires after launching Passion Projects were women. Horvath also said she’d noticed major changes at GitHub as more women were joining.

GitHub public relations representative Liz Clinkenbeard said that she was looking into the accusations and that the company would have something to share soon. GitHub has been valued at $750 million, after the social network for programmers got a $100 million investment from prominent venture firm Andreessen Horowitz in mid-2012.

Horvath did not respond to a query or give further details of her allegations, but said on Twitter she would be writing about her experiences in more detail soon.

The shift in Horvath’s tone is problematic for GitHub, because she had been a long-time defender of GitHub. But even in a January interview with ReadWrite about how progressive the company had become, she noted some lingering issues: “I recently got an email from a middle manager that began, ‘So Julie, how are the women at GitHub?’ I said, ‘You should ask them.'”

Indeed — the point she has been making on Twitter is yet another persuasive case that something in very wrong with the state of women in tech, which has been made elsewhere and more frequently of late and needs desperately to be aired.

The issue has spilled over into other Internet companies too, as Horvath quite correctly called out Secret, the anonymous-sharing app, for leaving up what is an appalling post about her, in which she is called “Queen.”

https://twitter.com/nrrrdcore/status/444646082857820160

The controversy calls to mind that of Adria Richards last year, an incident that exploded over issues of how to surface sexist comments. Richards was pilloried for her methods of pointing out the issue publicly rather than dealing with it privately.

That said, Horvath, who has been actively tweeting, just made the point that it matters little how women deal with such gender issues in the workplace.

https://twitter.com/nrrrdcore/status/444888841988485120