After searching the forums for an official list of forum ranks, I have come to conclude that not one exists. Therefore, I would like to provide all forum-goers with a list of the forum ranks and how to achieve them. For those who do not know what a forum rank is, allow me to explain that as well.
What are Forum Ranks
Forum ranks are a ranking system made for all forum members, based on the specific amount of posts a member has. Therefore, upon achieving a certain amount of posts, the member automatically upgrades to the next rank. Forum ranks are not to be mistaken as actual ranks, but rather "decorative" titles that show other members your dedication to the forums.
Current List of Forum Ranks and How to Achieve Them
Newbie - The rank which all new forum members begin with.
Jr. Member - Achieved by making at least 50 posts.
Full Member - Achieved by making at least 100 posts.
Sr. Member - Achieved by making at least 250 posts.
Hero Member - Achieved by making at least 500 posts.
Champion Member - Achieved by making at least 1000 posts.
Grandmaster Member - Achieved by making at least 5000 posts.
This is the current rank list and as of now, there is no guarantee that these are the only ranks or if other ranks exist, as no one has so far achieved a rank higher than Champion Member. At the moment, the highest post count on the forums is currently held by a very dedicated Nick3306 with a grand count of 3296 posts.
Ranks based on In-Game Rank
Guest - Not a visible rank. All new forum members begin with this rank. Has the ability to post, quote and modify their own posts. Holds 1 gold star under their forum rank.
Guest/Recruit - A rank given to all Classic Server Recruits. Has all the powers of a guest. Has the ability to remove posts of their own and report posts to a moderator. Holds 1 gold star under their forum rank. [This rank isn't always automatically given considering the vast amount of recruits on Opticraft. Recruits may ask a forum operator or moderator to be given this rank if not already recieved].
Builder - A rank given to all Classic Server Builders. Has all the powers of a guest/recruit. Holds 2 gold stars under their forum rank.
Crafter - A rank given to all Classic Server Crafters. Has all the powers of a Builder. Ability to have a custom title. Holds 3 gold stars under their forum rank. Can access Crafter only forums.
Classic Operator - All Classic Ops receive this rank. Has all the powers of a builder. Has the power to modify, lock, and delete any post on the forums. Holds 4 gold stars under their forum rank. Can access Operator only forums.
SMP Moderator - All SMP Moderators receive this rank. Has the same powers of a Classic Operator (see Classic Operator rank). Holds 4 gold stars under their forum rank. Can access Moderator only forums.
SMP Operator - All SMP Operators receive this rank. Has the same powers of a Classic Operator and an SMP Moderator. Holds 4 gold stars under their forum rank. Can access Moderator only forums.
Developer - All Developers receive this rank. Has the same powers of a Classic Operator and an SMP Operator. Can modify player's profile information. Can modify user groups (can rank players to any possible rank on the forums). Holds 5 highly distinguishable Blue stars under their forum rank. Can access Moderator only forums as well as Classic Operator Forums.
Admin - Only the Admins of Opticraft receive this rank. Has all the powers of a Classic Operator. They watch over the forums to make sure everything is running smoothly. Has the ability to post a Server News update. Has access to Adminstrator-only forums. Holds 5 highly distinguishable Blue stars under their forum rank.
Administrator - Only the Owner, Opticalza, has this rank. He is the forum site owner. Has all the powers of Admin, and more! Has access to Administrator-only forums. Holds 5 highly distinguishable Red stars under his forum rank.
Thanks for reading and I hope this thread helped all its readers! 
