WHY IS THERE AN OPTION FOR ADMIN TO READ MEMBERS PMS IS THIS ON ALL FORUMS AND IF SO WHY AS I NO OF ADMIN ON ANOTHER FORUM WHO ABUSES THIS AND READS ALL MEMBERS PMS SURELY A PM IS JUST THAT A PRIVATE MESSAGE
One reason is that all members can not be trusted to not abuse other members. Should a complaint be made by a member of abuse, the Admin can see for themselves, what was said and who sent the PM to the complaining member. This is another good reason for only one (1) Admin of a forum.
You have more than one Admin in your forum, so more people have access to the PMs of all your members' "Private Messages". The having more than one admin of a forum will possibly open the door for abuse of the "Private" needs of "Main" Admin's forum and under-mind all their work in having a nice forum that members will want to join and be a member of.
There is nothing wrong with a Forum Admin protecting their forum's best interest, by having access to the PMs of its members, unless the Admin cannot be trusted.
Members should use email to send a message to the other members when they are saying something they don't want to possibly get out to the "wrong" person(s).
It's not "Private" if the Admin allows it not to stay "Private" by giving extra people access.