Daniel, the cron job works and I do get moderation messages just fine. I am asking about user notification messages, and I did already test it with two non-moderator accounts. The user notification checkbox is visual and checked by the user. The first poster does not get a message that a reply to his post was posted by the sevond poster.
I am not sure where to look for the email queue. In my host cpanel I can open phmmyadmin, but I don't see anything there about a queue. As admin I do get emails from Joomla when a new user registers, so that comes from my system, not from ccomment.
So I am still befuddled!