What The Blog Staff Can Do
Blog Assistants can edit, lock, unlock, draft, and undraft blog entries, as well as unapprove comments and view drafted entries and unapproved comments. Additionally, if a blog author has their blog's settings set to "Approve Comments", comments by Blog Assistants (or any Admin/Global Moderator/Blog Leader) are automatically approved.
What can the Blog Leader do?
Blog Leader can do everything the BAs can. They can also pin blogs (like this one) and delete content blocks.
What can Global Moderators and Administrators do in blogs?
Global Moderators and Administrators can do everything the blog owner can do except make new entries.