User blog comment:Brandon Rhea/Wiki Modernization Stage Two: Page and Article Headers/@comment-26053883-20170316191056/@comment-20644-20170316192310

We don't actively support custom CSS, so there may need to be changes that are made. During the testing, though, we won't be allowing customization since we need to gather consistent data. Whether we allow customizations or not once the final version is released is something that we're still discussing.