|What exactly do you mean by ranks?|
On Stardock's forums (as with most), posters can gain ranks over time. The difference is that here, the ranks are not based on your postcount, but the value of your contributions to the forum and community. Over on the GalCiv2 forum, the ranks are as follows (it may be different here, or we may not use ranks-not sure what the plan is there just yet).
Exiles and Visitors are people who have been banned, the former permanently and the latter temporarily.
Citizens are normal users; this is the rank you start out at.
Veterans have earned a bit of recognition through their contributions, but don't generally get anything special other than the rank itself.
Diplomats and Ambassadors are valued and trusted members of the community who may get special access to private forums or beta test builds that are not available to the general public (at least, such is the case with GC2). FYI, those who were ranked Diplomat and above before GC2's release got their names in the GC2 credits, and most of their screen names were featured as ships in the campaign.
Governors and Senators are forum moderators, and may be volunteers or Stardock (and now Ironclad) employees.
Avatar is the final rank and is reserved only for SD employees, primarily the game devs and others directly involved with the forums in question.