Let users filter private messages by contacts/relevance
Recently a girl told me, as she apologized that she hadn't replied to my message sooner, that she simply couldn't keep up with all the insignificant and irrelevant junk messages that people were sending her.. - I thought it was simply that most recipients were ignoring me, but her description makes sense as a different explanation: I believe a lot of girls simply give up on reading their messages becasue their inboxes get overwhelmed with irrelevant stuff, and so messages of more relevant content tend to drown out in all the 'noise'.
Maybe it'd be a good idea if you introduced a way to filter incoming messages and the users who send them, so you could 'mute' or de-priotitize messages from users whose messates you don't consider relevant.
There will be users`s search in PMs instead