In the event of any theoretical legal action, all you have to do is hand over the material to the authorities, yes it is there and can be accessed if needed to be, but that is very different from knowingly installing a modification to read PM's or worse logging in as them.. what a horrible thing to do!
Sorry but I find it totally unnecessary and a violation of people's expected privacy. Snooping around "just in case" such things MIGHT be happening sounds to me like a pretty shallow excuse to go on a voyeuristic mission into your members private discussions.
I don't think anyon suggested here that admins are justified in going into Personal Conversations "
just in case things MIGHT be happening." It just hasn't been mentioned. Or perhaps I have missed something.
When I have gone into a Personal Conversation it is because a participant has deliberately reported to me that something has gone on which has caused unacceptable distress, or downright misleading and destructive information; or other indications of bullying.
Alternatively it has happened that someone has mentioned something to me without it meaning to be a "report." I find the reference to be unacceptable in the same terms - unacceptable distress, or downright misleading and destructive information; or other indications of bullying. I check and if all is well no one is upset. So far in all cases I found something of concern, except once.
In all cases I "own up" to what I have done. In the great majority of cases it is handled as an educational situation. The Conversation is placed in a document and the offensive parts highlighted.
There is also comment added to show that I understand why heated language or clumsy language was used, or whatever. In that way I get the offender to listen to me because they can see their position is respected as well as the other participant.
My comments explain exactly why there is a problem, and suggest a different way to express things without giving offence. (I am an experienced mediator)
I have found this approach is well received. On my more adult site I have only twice in 7 years had to exclude a member for persistently disregarding this kind of guidance (given 3 times in each case). On the younger community only one has been excluded.
A statement on Privacy is listed in the site Library, in our A-Z of guides. It clearly states that Personal Conversations are not 100% private but may be checked by me, and only by me, if I have reason to believe that someone is being rude, aggressive or misleading someone in a significant way. I add that I am far too busy to read PCs for fun and have plenty of ways to have fun in my precious spare time!
I have never had a single complaint about any of this. On the contrary I have been thanked for protecting a remarkably peaceful and courteous community by doing this kind of guidance.