@alexolut editors are already included, but close voters are probably omitted on purpose, so that user won't spam all five close voters with "plz reopen this" requests.
@username auto-completion for comments was recently implemented, and is already active on MSO.
However, it only seems to auto-complete the usernames of people who have commented on the post. According to this topic, the list of users who can be explicitly notified also includes:
Anyone who edi...