Mentions
A mention is a feature that sends an email notification to a specific user when you type @ + the user’s login ID in a text input field, such as the note field of an issue.
Mentions are useful when you want to notify someone who is not the assignee or a watcher of the issue.

Use Cases
Mentions are useful when you want to notify users who are not set as the assignee or a watcher of the issue about updates or notes.
Notifying users outside the assignment flow:
When someone is involved in the work but is not listed as the assignee or a watcher, a mention allows you to draw their attention to a specific note.Highlighting a message to a specific watcher:
If an issue has many watchers, you can use a mention to direct a question or request to just one particular person among them.
