Interesting conversation. I do agree that the wording could have been chosen better, or that some sort of additional info should be made available for that broadly generic “acting on you behalf” clause — e.g. in a balloon popup when hovering, or via a link to page explaining it in detail.
On the other hand, I didn’t really think much of it when I saw it during registration, the reason being that its purpose is clearly that of connecting the GitHub Community account to the main GitHub account. Since both services are provided by the same company (GitHub Inc.) I saw it as being merely some legal requirement on their side.
Needless to say, others might consider “legally suspicious” the request for the same reason — i.e. since the two accounts are handled by the same organization why asking for that specific permission? And, possibly, could this permission have effects also on the main GitHub account?
Personally, I actually appreciated the fact that I was being informed and asked permission to join the two accounts, and that this wasn’t simply done “auto-magically” behind my back — like it often happens with big corporations that provide many different services. But I’ve signed up using my personal GH account, and if I were using a company employer account I probably wouldn’t have consented to that without consulting the firm’s lawyer first.
Having said that, asking users to grant permission to “Act on your behalf” is indeed a rather perplexing request — and probably it might have turned away lots of potential users who , on reading that, didn’t consent and turned away. Chances are that there is no way to know this, since most of those who were deterred by that clause are unlikely to leave feedback about it.