I've commented on at least four WordPress related posts on Stack Overflow tonight only that don't even remotely belong to SO. Some belong nowhere since some users believe we'll just build WordPress for them.
I think SO should automatically suggest users to move the question to WordPress if it detects WordPress in title or tags or maybe even the text. Somewhat like the 'Similar Questions' and 'Questions that may already have your answer' work only that it should be in big bold red or something. I don't know what would work for this kind of users, but something needs to be done.