With the introduction of the unified profile for the Cloud products, there's is an option to change the nickname for a user and this will be used in products like Stride and Confluence, so the user can be mentioned through the configured nickname. In Jira, although the nickname has changed, the same is not used in Jira for the mention. Only the email, previously configured username and full name will be used.

This is a request to allow Jira to use the nickname from the unified profile for the mentions.