User blog comment:MisterWoodhouse/The first migrations to the Unified Community Platform/@comment-40240789-20200815221743/@comment-1869454-20200816043140

Our theme transitioned over (mostly) correctly. However, since then, about once a day "FANDOMbot" comes along and resets any changes we make through the ThemeDesigner, bringing us back to a vanilla wikia look.

Exactly how hard you'll be hit by the feature loss depends on the features you're relying upon. Your page code should stay in place, if that's what you're worried about.

NoReplyz has set up a list where you can get an overview of many of the problems which may affect you.