Compare the default summary of an edit on sections of [[Wikipedia:Sandbox/Subpage]] with the following headers:
(1) == [[Wikipedia:Sandbox/Subpage|Subpage]] ==
(2) == /Subpage/ ==
The autosummaries were the following in each case:
(1) /* Subpage */
(2) /* /Subpage/ */
The second one is wrong and should be equals to the first one, just as happens with the displayed text of the corresponding links.