Unable to Use @Mentions in a!eventHistoryListField

Question

Hello Everyone, 
 I am facing an issue with the Event History List ( a!eventHistoryListField ). I am not able to mention/tag users (using @ , for example @ABC ) while adding top-level comments. 
 Has anyone used this feature successfully with eventHistoryListField ? Any inputs or suggestions would be really helpful. 
 Thanks in advance! 
 Regards,

Stefan Helzle · Answer

Did you configure the "mentionableUsers" attribute?

Shubham Aware · Answer

@mention for top-level comments only when eventStyle is set to the Comment List style, allowUsersToComment is true on a!eventData(), and mentionableUsers is populated with the users or groups allowed to be tagged. Only users within mentionableUsers will appear in the @ picker and receive email notifications when mentioned.

Shubham Aware · Answer

Yogi Patel said: Can we configure or customize the email subject? 
 No configuration available. 
 Yogi Patel said: How is the word "Expense" being populated in the email body? 
 That comes from the title configured for the event record.