Here's a quick note about the stars. Right now, they're just a direct replacement of the labels that we displayed for each level.
They had been:
Aspirant
Contributor
Journeyman
Authority
Guru
Oracle
We updated the Journeyman and Guru names, and displayed stars instead of labels for each level. It took me months of working here to remember which label stood for which level, and I saw many times people thinking someone's name was Journeyman or thinking they were an author because they had a Contributor status.
Tweaking the stars for the levels is something we can certainly look at in the longer term. For right now, we think it's an easier way to display the participation level of users without relying on terms that may not be familiar to all of our users, especially the international users.
For the top users, we added the condition that they have at least 25 mozpoints. Previously, if someone had one mozpoint and logged in within the last 60 days, they were listed in the top users. Now they need to have at least 25 mozpoints to show up on the list. There are only 20 points possible for filling out your complete profile, so now the people on that list have actually made some type of contribution (usually a comment or Q&A question) to the Moz community.
I hope this helps explain the stars and points a bit more for everyone!