Do you ever get invited to join a "Yahoo moderator" and what' up with that?

The moderators on this Yahoo Answers site are us -- all the users. It is 'community moderated'. What you are seeing is SPAM emails or messages of some type. You should either ignore these -- or report them. Yahoo can't be aware of and block ALL these types of things, so they rely upon us to make them aware of things so they can take care of them.