many forums have these and even wowhead has them off their forum. i know they'll add more flavor to posting, your profile, your contribution, contructivity and loads more. we have one achievement already that changes with the amount of posts you have. let's add little badges under your profile let's take a look at this example:
X = Badge 1 icon
Y = Badge 2 icon
Z = Badge 3 icon
... = Click to see all of user's earned badges.
Profile:
Post Count Achievement Name We Have Now
X, Y, Z - ...
Location
Post Count
An example of what some of the badges can be. This time let's add a name to a badge.
(Weekly Freaky): Posted consecutively for an entire week.
(Stomraged!): Posted 10,000 times.
(Battle for Azeroth!): Logged in during Battle for Azeroth's launch week.
(Trendsetter): Original Poster of Thread that reached 100 pages.
(MVP): Make 100 friends
These are purely for cosmetic purposes and can be used for other things.