I can't much add to the substance of what Sammy said, but I can give you some Moderator history.
The first Shark selections were made by the owners. However, by the time that Kris became a shark, I believe the owners were taking members' preferences into account. In the past year, however, either the owners and/or moderators have been making Shark selections based on many factors which Sammy precisely detailed.
As for the ranking aside from Sharks, it is simply a matter of # of posts on the BB. Implying, I believe, that there is value placed on member longevity.
As for Salty’s description of the Shark Tank....he is right on the chum! The Shark Tank is an extraordinary place where the waters are deep blue and the feeding is great! We do have an occasional Shark Attack in there [You can only imagine what its like with all these male Sharks!] but I , exuding a calm, stabilizing, and not to mention charming, influence in the Tank, am able to keep things pretty much under control with all these feisty he-Sharks. LOL