Look at the forwarding which is already happening. They are already giving that big company the emails. That big company gets a copy of every email which is posted publicly already.
Are you concerned about their privacy policy? Are you concerned about them complying to a government demand or ads.. What's your exact concern here.. Keep in mind that github has access to your data and their EULA probably allows them to run whatever analysis they want. A that the high level it's essentially the same thing. The difference is that github isn't smart enough to tie revenue into this. (Such as displaying ads to C/C++ devs) "we" (most technically savvy people who own a smart phone) can't avoid these big companies. It's just a fact of life. For a small organization like gentoo - it should be respected when time saving choices are made that allow everyone to just get things done. I hope "social contract" doesn't mean zealot and instead means someone who is pragmatic... What's the real concern here.. pragmatically. (honest question)