Well after a moderator application is locked, you can still rate the posts. I think this should not be possible, as it could just lead to rate abusing and there is no reason why people should be rating locked moderator applications.
I think it should also be made procedure that when I thread is locked it should be immediately archived, I see lots of locked threads in Discussion, etc. If nobody can post in them, they should be in the archive and not in the public forum.
Support. I think that all posts, once locked, should not be able to get ratings because I usually delete posts that i don't want ratings on. I wish that some of those posts could have stayed around.
Locking means their question has been answered or the owner of the thread requested a lock. If the owner requested a lock of their application they either want to make a new one, or decides not to apply for staff anymore. Locking it makes sure no one can comment unless the thread is unlocked.
If anything else is locked, not an application, it would be moved to archive and locked. Applications would not be removed since there is no reason to remove them, people can still look at them and things. If you request a lock on your application, you can request for a moderator to unlock it too, so you can have a conversation. I know what you are thinking, I had the same thought a couple months ago. Applications just locked is fine, every other topic has an archive area where all locked threads get moved, I believe.