carg What you sometimes also see is that PM is only available between 'friends'
This is an option if it possible to realise.
As @Laura wrote the Moderator can contact member via PM for clearing any dispute or cal a warning. This should not visible to someone else.
If someone want to contact another member he can ask the member if it ok that @Laura send the email address. It worked fine in the past and prevented that it was asked lightly but only after careful consideration. Most of the conversation is still at the forum whereby some not suitable done in private.