Please would someone enlighten me as to what the various star options mean?
Nothing more than the more you post, the more stars you get under your name with a maximum of 5 stars. 6 if you're a competitor.
Purple colored stars mean you're someone "special".
Pro, competitor, expert, etc.
It's broken down something like this...
500 posts (2 stars)
1000 posts (3 stars)
2000 posts (4 stars)
4000 posts (5 stars)
I could be wrong, but you get the jest of it.