The description about covers it--if you disable a button, for example, it doesn't get grayed out.
(Menu peers do seem to work, however)

The description field as copied from bug report 1257852 follows:

1. Select Pages: Show all pages

Result: The Delete key for the "Remembered" and "PagesMenu" lists is not greyed out even though no item is selected in the list.
NOTE:not happening on Solaris.