I received an email today that an update was made in a discussion to which I had recently posted. The email noted that if I did not want to receive further notices, I should follow the link to edit my settings.
Perhaps this notification feature is newly added, amd the flag on everyone's user profile was defaulted to "yes?"
I found the spot to change the flag without following the email's URL but rather via the "my CHOW" and "edit settings" links. I unchecked the box and clicked the Submit button. The page displayed an http 500 error.