Here is the right thread for your question.
https://bitcointalksearch.org/topic/forum-rankspositionsbadges-what-do-those-shiny-coins-under-my-name-mean-178608
As For newbie , member , full member and so on
This forum has activity period : 14 days, if you have at least one post within that period your account will gain '14 potential' activity.
For example, you register today and you make 15 posts in your first day : your rank will be newbie and your activity will grow till 14. Within that activity period you make another 10 posts, still your rank : newbie and your activity : 14 and post count 25.
Now next activity period arrives, on that day you make only one post : you will get activity 26 and your rank will remain same.
In 3rd activity you make another post, now you will get chances for your activity to grow up to 42. Here when you have 30 or more posts, you will get your new rank Jr. Member.
Similarly, when you will have chances to get activity for 60 and if you have 60 or more posts you will get your Member rank.
Hope this helps.
Much better . Thanks Guys
There's also a time limit added to users that substantially decreases.
I think it starts at 6 minutes (360 seconds) for less than 10 posts.
But then decreases to 5 minutes (300 seconds) and continues to decrease (I think for my rank, It's every 30 seconds it decreases too)!