To be clear, I find the emails very useful (this is primarily from the perspective of me using Github for work--it's nice to know when somebody has reviewed your code). But I want one, not 15, and after the code reviewer has finished.
I agree this is a big problem. I've had cases where I'm still reviewing stuff but the person whose code was under review just fixed my first few comments and then submitted it while I was still writing the rest.
I know this is partially a process problem, but having batched emails would certainly help make it more obvious.
Google's reitveld is a bit of a mess but at least it gets this part right.
You can. I had to do this because my GitHub username (like my HN one) is just my name ("rob") and I was getting notifications from people using @rob in their comments/replies instead of the person's actual GitHub username. :)