Last modified: 2014-07-08 16:22:56 UTC
See this edit: https://www.mediawiki.org/wiki/Special:Contributions/Jorm_(WMF)?offset=20140421174238&limit=1 I'm assuming this was caused by Flow. The edit summary seems to directly include block-displayed elements including both a <p> tag and a <pre> tag, disrupting the flow of the contributions list.
*** This bug has been marked as a duplicate of bug 67546 ***