I have decided to disable this group. It already hasn't allowed posts by members for a while, but it has still served as a notification system for GitHub and for certain issues in Google Code (namely, those with NeedsReview, NeedsBetterPatch, or PassedReview labels).
GitHub has since added their own mechanism to do this. If you want to receive updates on all comments on SymPy related pull requests, go to repos you want to watch from https://github.com/sympy and click "watch" at the top. If you have push access, you should already automatically be watching each repository. If you want to unwatch a specific pull request that is too much noise, you can go to that pull request and click "Watching Thread" at the bottom and change it to "Mute". Note that you will automatically be set to watch specific pull requests where you are @mentioned by your username. If you want me to ping you on pull requests of a certain nature, just let me know and I'll try to remember to do it.