So I think this may be a bug:
I appear to have achieved the
comment everywhere privilege with 49 reputation.
Not a huge problem, but a curiosity... Do I report this or something?
You probably down-voted answers right after you reached 50 points, or you got some of your posts down-voted. Once the system notifies you about a new privilege, there isn't any way to remove the notification if you lose reputation. Probably, they could add a delay on notifications for new privileges, but then there would be users complaining they aren't notified when they get new privileges.