Drop a nested portlet onto a page and put some child portlets in it.
Attempt to rearrange the child portlets within the nested portlet OR
attempt to move the child portlets back out of the nested portlet.
In either case the child portlets can't be individually selected. Only the parent 'nested portlet' can be selected and dragged.
This works in 6.2.2 GA3.
Tested in Chrome and IE.