In User Control Panel → Board preferences → Edit notification options, the system is currently displaying three columns of checkboxes, "Notifications", "Email", and "Notifications" (yes, again).
From testing, it appears that the third column (the second "Notifications" is erroneous/non-functional, as any of those boxes you check will be lost when you hit "Submit". So, it's purely a display issue... but it is rather confusing, and based on some older screenshots that users had posted in this forum I get the impression that it's a relatively recent thing to have cropped up.