There is no username popup suggesting completion when typing an editor's user name prefix.
Steps to reproduce:
- Find a post by AUser that was edited by UserB
- 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.
The Meta post on this feature states; while referencing this answer:
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. This is why I classified this as a bug.