First Item,
There is not a need to lock a global announcement.
Nobody can reply to one, other that a admin or the creator.
I consider that a bug.
That is why at this site you see a global announcement with a link to another post for replies.
But I Believe a global moderator can edit one if they have permission to do so.
Not sure about a regular moderator, since they have access to only their forum and the announcement may be from a forum they don't have access to.
