One workaround would be to remove any public email address you commit under from your Github profile. Github uses these email addresses to tie back to your user profile so if you don't want commits pointing at your profile, don't tie email addresses to your profile.

Perhaps some mechanism is called for here for approving tying back to your user on new repositories or making any repository not owned by you or your organizations require an explicit opt-in to tie back to your profile.

Edit: This is kind of the equivalent of spoofing the From address in an email.