Double .panel class on confirmation page (ajax error?)

On post approval confirmation page instead of message text there is mysterious entire HTML form wrapped into .panel class.

Bug is not visible in prosilver because in prosilver .panel class does not have any layout other than background color and border radius. However as soon as some styling is added to panel, bug appears.

I've attached 2 files: screenshot of bug, DOM structure. In DOM structure screenshot fieldset element that is highlighted is supposed to be a paragraph. Code in confirm_body.html is correct, so looks like some ajax shenanigans are going on.