Testing with openfire 4.8.3 and Monitoring plugin 3.6.1
Assume two users A and B. A and B have joined the same anonymous room. They have both sent each other 2 private messages in the room. They have also opened a private chat and send each other 2 direct private messages.
When user A sends a query to his own archive (to:A) and specifies a with critirium for B (with=B), the plugin returns 6 messages: 4 private and two whispers, the private messages sent by B as room participant. In fact those are the two messages which user A should not be allowed to know that they were send by B, because they were send by the B room alias.
It does not matter if the room was not anonymous, the result is always 6 messages, so either their are 2 message to many or 2 are missing (the private messages A has sent to B in the Room)
I had a look in the code, but this only added to the confusement.