I'd ask for the source thread to be moderated. That's usually less work for the staff in these things.
"You may submit a post for this thread if it's a source. If your post is a source it may be added to this thread. Otherwise please post *here* to discuss items in the source thread."
"You may submit a post for this thread if it's a source. If your post is a source it may be added to this thread. Otherwise please post *here* to discuss items in the source thread."