Shouldn't users with move permissions on specific forums only be able to move threads between those specific forums? For example, right now I have a group which has the ability to move threads from a "pending applications" forum to a "completed applications" forum. However, these admins also have the ability to move threads from the "pending applications" forum into my "news and announcements" forum which shows up on the front page.
They don't have the ability to create threads in that forum, they don't have the ability to move from that forum, so it would probably make sense that they shouldn't be able to move INTO that forum either.
Short version: Thread move permissions should probably be checked on the "to" forum, as well as the "from" forum.