I wonder if an account will be allowed to unmute/unblock an account, in order to downvote (block) it again in later posts. Otherwise you're looking at using a lot of blue checks to silence articles from say, NYT.
The question of thresholds is interesting: if it required a large number of votes it wouldn’t be very effective. If it doesn’t, it’s too easy to game — and even a million accounts doesn’t seem like a high bar since it could easily be rented for many votes. A large ad agency or PR firm could do that - promising all of their clients the ability to bury bad news (thinking of how much Johnny Depp alone paid) – and it’d be really easy to imagine, say, the Catholic or Mormon churches, Scientology, etc. recruiting members or even funding their Twitter Blue memberships.