App Review appears to be more strictly enforcing rules regarding the use of Apple intellectual property in third party apps, which now includes emoji. Developers are reporting that their apps are now getting rejected for using the Apple emoji icon set in screenshots, other marketing and parts of the user interface (such as using emoji in place of custom iconography).
As described to Sam Eckert, apps cannot use emoji outside of places where a user would have typed it in to comply with the new rules. Apps must replace usage of Apple emoji with custom icons, or nothing at all, if they want their app to be approved.
As always with App Store stories like this, the App Review team has shown itself to be inconsistent in interpretation and enforcement. However, Eckert’s tweet is not the only account we have heard with a similar story on this new anti-emoji policy.
Apple has not added an explicit mention of allowed emoji usage to its public App Review Guidelines yet. It seems the reviewers are banning their usage under other clauses relating to misuse of Apple intellectual property.