Steps to Reproduce
In a Eureka or Fuji instance, navigate to System Localization and click Enable I18N Debugging.
Navigate to System Properties > System Localization.
Check Displays translation prefix on translatable strings and click the MSG: Save button.
Navigate to System Localization and click Disable I18N Debugging.
Go back to System Properties > System Localization and note that the prefixes still display.
The same issue occurs for watch list fields in a form.
Review the changes and remove the prefixes from the labels. For fields like Description and so on, flushing the cache, logging out, and opening a new session clears the prefixes.
Related Problem: PRB674685