The watchlist links diff and hist are mis-nested HTML: they are a <DIV> within a <SPAN>:
<span class="mw-changeslist-line-inner" data-target-page="Wikisource:Scriptorium"> <div class="mw-changeslist-links"> ....links </div> .... </span>
This is invalid HTML, since it's a block element inside an inline one. The W3C validator reports this as an Error.