Sorry, I forgot about this when I was deploying and had to scramble to implement the last few details.
The word "privileged" is no longer really an accurate description of what the account level is. They have a couple of perks and enhanced search options. They certainly don't have unrestricted uploads.
As cliche as it is, I think "gold" immediately conveys what the account is: a paid upgrade that improves your Danbooru experience. Platinum accounts are along the same idea. They're just a way for me to add price discrimination.
So clear it up: gold accounts are privileged accounts. Platinum is one level above that (but still below builder) that I haven't quite figured out yet.
In terms of what this means for existing privileged users: I'm going to try hard to make sure the experience doesn't change for you guys. The account upgrade page says there are caps on favorites but I'm wavering on this and the caps aren't implemented yet. I mainly want to prevent abuse (people who favorite 10,000+ posts). The primary advantage of a platinum account right now is the ability to search up to 12 tags at once.