What does "post number building" mean?
I saw a post of someone was deleted by a mod, who gave the reason- post number building.
There may be some privileges that you gain after losing your "new member" status. This status is based on the number of posts one has made.
If you post a bunch of posts just to get your numbers up to change your status, then you are in effect gaming the system. You are trying to build up your number of posts.