Rating/filtering posts ala slashdot

[Neil]

I have problems on my forum with people making idiotic, but not necessarily rules-breaking posts, such as the following:

"Well happy birthday. i guess my gift to you is a.....uh...... A BIG SPEAKING GOAT NAMED PHRED! he cannot read though and once ate a small child so i suggest you keep him out of the house."

Obviously this is just wasting people's time to read, but I don't want to delete such posts because it would appear to dictatorial and violating "free speech".

What I would like to do is be able to rate each post on a scale of 1-5, similar to the way that slashdot moderators rate posts on their threads. Then a user can set in their preferences what rating level posts they want to see, and filter out anything below that. It would obviously be necessary to override that on a thread by thread basis, and it would also be necessary that unrated posts (cos I havn't gotten round to it yet) are always displayed (or perhaps that's another option in the user's settings?).

Hopefull this will bring back good posters who don't like wading through the crap to get to the good posts, and may discourage idiots from posting without thinking.

Does such a hack exist? If not, can someone write it please?

Thanks for your help!