Given all you have tried the only thing more I could say is trust cafe by the wikipedia guy. Unfortunately its not federated but it does have this neat thing where you can rate everything. Its basically like nuanced subscribe and block. You rate things between zero and 100 and I think zero would effictively be the same as blocking (which you can still do) and 100 would be the same as subscribing (which you can still do). Everything by default starts at a rating of 50. So its like you can be. mmmm. I like this guys post I will move him to 60. Or this guy seems a bit annoying I will drop him to 40 for now. Then over time the blocks and subscribes come out naturally.