[Brandon Martus]

I should've looked harder:

From vBulletin.com forums:
Bright green dots are better than dark green dots and the more dots you have, the higher the reputation. Having any bright dots at all means you have a higher reputation than someone who only has dark green dots. Same thing with the red dots, just in reverse.

The maximum number of dots you will see is 11 (in the current system).

Reputation

-99 to 0
0 to 99
100 to 199
200 to 299
300 to 399
400 to 499

Once you hit 500, you will start gaining bright green dots on top of the 5 dark dots but it takes twice as much to gain a bright green dot.

500 to 699
700 to 899
900 to 1099
1100 to 1299
1300 to 1499
1500 and up

Negative values work pretty much the same way except it shows balanced (grey dot) from -99 to 0.