neither reddit nor the various steem forums demonstrated any use in downvoting

i think web of trust based filters that include biases based on muting will solve most of the problem... 90% of asshats aren't in the second and third levels of your follows follows and the remaining 10% can be muted and this mute can bias the weighting to filter those out as well

i used to be on the hive forum, which was one of the pioneers of the concept of karma points - note that bitcointalk also adopted this... but it entirely depends on the quality of moderation and any way in which filtering posts gets too tied up in the control of a small number of people you have a lever that spooks are going to use to steer the conversation by being the mods or controlling the mods and ... fortunately this is mostly a client side thing

we don't want dumb, gameable moderation systems, the user needs to have absolute control, and any help they are given should be ONLY from those they already follow, thus web of trust > all 

 I'm not sure we need an algo to weight notes by downvote and I'm note sure any really do right now. But it's still something I personally would like to see. If something is spam downvoted, it can be pretty easy to tell.  

 You should try facebook.