Updating a field formatter at Manage display fields does not save the change, and the user is not warned of this

On a field editing page such as admin/structure/types/manage/article/display, if someone drag-and-drops to change the order of fields for a display, Drupal puts a very clear notice:
* Changes made in this table will not be saved until the form is submitted.

If someone clicks the cog button icon to change the display of an image from the original image to the medium image style, for instance, and then presses a nice button labelled update, the user has every reason to think the change is saved. It isn't.

Compounding this usability bug, the tabledrag notice disappears after you have edited a field display setting. [Potential separate bug: in one case after dragging a row, i was no longer able to get the cog to open the formatter settings, but i was not able to reproduce this.]

Minimal, non-string changing fix: Have the table drag warning appear whenever update is pressed in the settings for a field display.