The "sub-name" is called a Custom Title. Only the administrator can add/change/delete a custom title, not the moderators. Typically, as was pointed out earlier, you earn a custom title by posting something....unique. The administrator then, with his warped sense of humor, tags you. Once you have a custom title (or are a designated contributing member) your post title (100+ member, 500+ member, etc.) ceases to update automatically and has to be done manually. Again, only the administrator can update post titles.
The administrator is pretty busy with since the birth of his son and the physical move of his office, but he will eventually get to updates.