Your customer has built a mature knowledge base, with articles targeted to internal audiences, which...

To satisfy the requirement of identifying which knowledge base articles are visible to the callers from the Incident form, the feature ‘Show User Viewable’ would be used. This feature allows agents to see which articles can be viewed by the user associated with the incident. It helps in distinguishing between articles that are meant for internal audiences (technical) and those written for end users with simpler instructions. When an agent is on the Incident form, they can use this feature to filter and display only the articles that the caller can view, ensuring that the agent is aware of the information available to the caller and can guide them accordingly.

References: The answer is verified based on the ServiceNow IT Service Management documentation and resources that discuss knowledge management features and best practices123.