Only show all comment settings when not disabled

It annoys me that when I disable comments for a content type, I still have to scroll through all the settings to get to the Submit button.
It'd be nice if there was only one setting for Comments: Default Comment Setting (disabled, read only, read/write). If you chose to enable comments, the rest of the settings would appear. And the same in reverse; if comments are enabled and you disable them, the rest of the settings disappear (I figure some sort of jQuery/AJAX).

Sorry if this is already in 7. If not, it shouldn't be too hard to add :)