Hiding information and blocking opinions is horrible - allow me to just say that to start. Back in the olden days, it wasn't quite "troll rating" but a douche baggy trick whereupon you would give someone you didn't agree with a 2 or 1 or something to silence them or at least punish them into being more quiet with their comments incongruous with whatever the flavor of the topic was. It amounted to a tyrannous majority censoring people.
Sometimes, however, diarists (with or without malice) take it upon themselves to write inflammatory and controversial things - things which commenters shout "DELETE!" but, you know, they don't have to. It's like we have two choices: either promote a diary up or let it fall off... what we cannot do is judge it to be so devoid of merit and so inflammatory as to hide it like we can do with the comments.
We troll rate comments, right? Trusted users and all that. I myself have never worked hard to obtain "trusted user status" and the few times I've had it (when work and life and family let me blog more) I never used it. That being said, this whole issue regarding Palin's family is reason enough to recommend a "Recommend for hiding" button such that only trusted diarists can read or view these things.
Not delete them, of course, just hide them from your average Jose that wonders in here. It also will help with the GOP diary trolls.
Just my two cents.
It may be a bad idea, but it may be worth a trial or something.