Even I wonder about that
I believe at about 100 you become a copper member, I can't remember how many posts you need to have to become a nickle member (but it's definitely under 300). All the others such as silver, gold, platinum ect.. I don't know.
But you don't really need worry about having stars, I never seen anyone here who actually pays attention to them
the only starts I care about are these:
they look super cool and actually mean something.