We deployed a release on Tuesday that turned on an flag for all new projects. Unfortunately in some cases this has been turning it on for older projects as well, for those that have been created before the existence of this configuration option.
This may have affected the look and feel of your documentation sites, and caused some things to break in unexpected ways. We're in the process of rectifying this by writing a migration to disable the flag for all older projects and setting the default value properly.
Will update this when the process is complete. Email email@example.com
if you're affected by this and have any questions.