Exchange Online allows users to add personal retention tags to their maiboxes through OWA settings. Some organizations don’t like this, so they can deploy user role assignment policies to block the feature. It;s something that you could consider doing if you’re preparing to switchover to Office 365 retention policies to impose the same retention regime across multiple workloads.
A little known fact is that you can use graphic symbols and characters in Office 365 labels. It might bring a splash of color to your compliance and retention efforts, especially in a world where emojis are everywhere. After all, the symbols are just character codes that computers can process and Office 365 is designed to be multilingual and cope with different character sets (like the way Teams deals with Hebrew and Arabic).