Rob, I agree with your points on the padlock symbology vs the cross.

Just some clarification: The Closed marker has always been (and still is) a button, in fact it is the "New Post" button with restricted access. Whether or not you see the "This thread is closed" message depends on the user's access level, i.e. moderators can still use the button to post into a closed thread.

As has been stated before, the forum functionality has not changed one bit with the new skin. It's only the way things look now that's different, they still work the same as before, whether that's good or bad.