Since Hudson 1.349, console notes can be embedded into the console output file. These notes are stored in an encoded format and are intended to be stripped out before the console is displayed.

capn_carrot reports that the console notes appear in the file names reported by the Warnings plugin.
http://issues.jenkins-ci.org/browse/JENKINS-7402?focusedCommentId=141552&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_141552