There have been times when I have edited a post, left no comments, yet I have made mistakes that were pointed out simply as @comments. That's ok, but unless I actually come back to the post, I will never see that comment. Would it be possible to extend the comment reply functionality to also include the post editor? This might prove useful for some.
edit: this is now implemented.
We do a simple reverse chronological walk of the latest "action" by any user with a valid displayname in the post -- where "action" is defined by any sort of edit or comment.
So you can now @reply to editors of a post even if they haven't commented.
(and just as a gentle reminder, you don't need to @reply to the post author as they are ALWAYS notified of any comments on their post.)
A bit long for a comment, so here's my thoughts on specific ways this feature would be useful.
Most of these comments will be "correcting" a previous editor, such as "tag vandalism" (popular examples being [belongs-on-*], [possible-homework], etc.). When I see that, I rollback myself, but it would be nice to just leave a cordial remark and perhaps a link to meta about why their action is generally frowned upon. But they might also be correcting content of the question as John's example shows, which is less meta.
There are also worse cases. For example, JoshJordan's edit went far beyond removing offensive text in order to make a joke at the OP's expense, and no one has any way of mentioning to him why that is counter-productive. (And it's especially heinous given the frustration that user was already experiencing.)
Some of these comments will be simply asking an editor why they did something. For example, a user, especially a new user (but then they'd have to already understand @user), might not understand an edit, and I'd certainly reply to them if they asked, in the interest of improving the SO community (if only a little bit). But I'd have to find their comment towards me first.
Both of these types of uses are meta-discussion, but I am not suggesting to keep meta-discussion on SO: a comment seems the appropriate way to include a link to meta and complete the circle as appropriate. In other cases, a short note.