They are a quick visual guide to show how prolific a poster each person is.
1 pip = 0 posts or more
2 pips = 10 posts or more
3 pips = 50 posts or more
In time, I can change the pips to something more interesting and/or increase the number of levels. I can also alter the titles (currently newbie/member/advanced member) to include more options and/or more interesting titles. I may set it to allow those who post a certain amount to choose their own rank title.