discussion only with certain moderators or author

The private comments are visible for high level users. You can uncheck it for some user roles using the "User roles can moderate private comments threads" option. 

Thank you. Can one have a discussion with only a select few of all the people with mortaring role? Say you have 3 moderators but I want to have a discussion only with two using the @someone function, please? This would be very useful feature to have.

Or the message is sent to all the moderators irrespective?

and finally, can a moderator role be set to someone who hasn’t got post/page editing permission? 

thank you very much again. 

So, comment moderating roles can only be assigned to people with page/post editing permission, please?