When viewing a diff that contains empty context lines (gray), those lines are not shown. This is due to all cells in that row having no content, which reverts the row height to zero. It used to show a thin gray line, but a change in diff.css (table.diff td {padding: 0px;}) made that disappear as well. Example in URL should show an empty line directly above "==Professional acting career==".
Having the following CSS in your own stylesheet restores the empty line:
td.diff-marker {height: 1.5em;}
However, that is a hack; A better solution is not to have rows with all empty cells. At least one cell needs to have content, and all rows start with a cell with a diff marker; these are either empty, or contain a + or - sign. I suggest putting a non-breaking space ( ) in the empty diff marker cells. This will cause the row to have content and force the proper height automatically.
Version: unspecified
Severity: normal
URL: http://en.wikipedia.org/w/index.php?title=Matt_Smith_(actor)&diff=next&oldid=392393612