The actual requirement for the badge is for the youngling to post on the guild bb. Even older players occasionally post items on the wrong board- and new younglings are just more prone to make this mistake, or don't read the directions that are listed under the badge requirement completely.
From the BADGELIST help file - \"The individual is able to use says, tells, messages and understands the distinction. Also successfully posted a first bulletin board message on a board that is NOT the public BB and written/posted a letter. \"
Written by my hand on the 3rd of Ilmarael, in the year 1310.