User blog comment:DaNASCAT/Technical Update: April 11, 2016/@comment-24258073-20160412053139/@comment-452-20160412202811

"I still want to see people demanding a fix for edits that repeat the same categories every time someone edits a section of the page, which is really annoying because one doesn't know if the category was already on the page or it was introduced by the edit, polluting diffs and making category maintenance harder"

Woah, Wikia Staff have told me: "you seem to be the only one reporting/reproducing this issue."

So it's great to know that someone else is bugged by this bug.

It's been 4 years since I first reported it, and the lack of fix for this is one of the many reasons I don't bother reporting new bugs.

My first support ticket about it was 2011-12-29, but here's here's public proof that it's been happening for 4 years