Each user on the LEGO Message Boards has a profile. It allows other users to identify who has created the post they are reading. It consists of 8 things: the username, posts, likes, activity feed, avatar, rank, Join Dates, Badges, and their total number of posts. It is not possible to customize the profile, apart from the avatar, which can be edited under the "Edit Profile" button, underneath where you sign in.
In every User's Profile, there is a date saying when they joined. This puzzled users for a long time, because they had really joined LEGO.com before this date. In 2010, a user finally realized that it was the date of their first post. However, some users have a glitch related to this, and the date is actually earlier than when they made their first post.