Report Private Messages as abusive

[RoGGa-loves-DCSS]

When receiving an unsolicited private message, it is only possible to block an (ab)user from sending the receiver more PMs. The little red X should also allow for the option to report an abusive msg just like it is possible with posts. That way, cyber bullies and trolls will not be able to use PMs to continue their disrespectful ways since moderators will be capable of seeing a pattern of reported abusive PMs.
Just one of many ways to counter the growing Internet culture of hate.

[davidpanderson]

This would be a fairly large change; the moderation system (DB structure and PHP code)
is only for message boards, not PMs.
Easier thing would be make a page (visible to admins) showing most-blocked users,
letting the admins look at their PMs and optionally block them from sending PM to anyone.

But is this an actual problem on any existing project?