There is no username popup suggesting completion when typing an editor's user name prefix.

**Steps to reproduce:**

1. Find a post by AUser that was edited by UserB
1. Write a comment addressing `@UserB`

**Expected results:**

When having typed `@U`, the completion popup should suggest `@UserB`

**Actual results:**

No popup, as if there were no such user in the list of addressable users.

> ![enter image description here][1]

---

[The Meta post on this feature states](http://meta.stackexchange.com/questions/43019/how-do-comment-replies-work/43020#43020); while referencing [this answer](http://meta.stackexchange.com/questions/36052/allow-post-editor-to-see-comments-directed-at-him/36055#36055):

> Notifications apply to the author, commenters, and editors of the question or answer that you are commenting on—users not in that list cannot be notified. You can also notify a ♦ moderator who closed the question. 

The popup can easily be seen as an indicator whether the user whose name I'm typing will receive my message, since, while typing a user's name and the name disappears from the suggestion list, it means I mistyped and the user will not be notified.

This behavior suggests that editors will not be notified at all, [while they actually are](http://superuser.com/questions/252673/asus-eee-win7-x86-service-pack-1-failure-code-80073701-unknown-error). This is why I classified this as a **bug**.

  [1]: https://i.sstatic.net/i0wt0.png