By Leviathan.Webjester 2008-08-05 12:22:02
The Character data (including rank/title) is pulled from the Playonline Fanzone site, which does not currently list Captain as a Mercenary Rank. It still, currently, will only display First Lieutenant even if you've finished Captain.
Hopefully Square will get on the ball and list captain as a rank as well as a title. But judging on how long it took them to get the new items from the March update, it may be a while (if at all).