User blog comment:Acer4666/Theme designer, not css/@comment-2093602-20110730192245/@comment-1066636-20110801122156

Well, I'd understand it as "if you use custom CSS and we have to make changes which in turn break your custom CSS, it's your own responsibility to fix your custom CSS" - which is perfectly reasonable to me. Otherwise Wikia could either never change the site-wide CSS/HTML, or would be majorly bogged down by having to go around and fix people's custom CSS.