Yep I think your week off cost you here :)
Love me some nested selects for readability!
The issue is seemingly a lack of key to main post from the comments within.
Also, a comment has a depth > 1 and a parent author, but nothin to say it is a comment of this post which was written by this author.
Anyway, string query saves the day!
Good old string query, almost sounds like a sitcom!! :OD
I must try harder in the other commenting!