Board Thread:Support Requests - Getting Technical/@comment-1187559-20150726144220/@comment-1038387-20150726145104

It means Enhanced Recent Changes was activated. Wikia's been doing some things to preferences lately, and you should be able to set it back in your preferences. Under Under the Hood, check if there's a tick under "Use advanced recent changes". If there isn't, tick and save. I had a similar issue with Grouped Recent Changes a week or so ago, and then, unticking that box didn't help. That was a bigger issue. If it persists in your case, use Special:Contact/bug.

To counter what Lucario said, this is not a change, this is something that has been available for some time. It's just that your preferences seem to have been changed accidentally.