Who can be @mentioned in comments for JIRA Software?

[Srikanth M]

Reporter, Assignee are possible to mention them by @Reporter or @assignee say, in comments. We have a custom user picker field 'Initiator'. 

One of our users wants to know if there is a way we can use @Initiator too where JIRA replaces it with the value in the Initiator field just like with reporter or assignee?

Thanks.