So have the button say "Trust this person's feedback" to make it clear what the button does.
Exactly, and as an earlier poster said, this "Trust" thing is kind of unnecessary when you could just lock in the opinions of people whom did transactions with you by agreeing through the forum to exchange feedback on transactions. Press a button, agree to contract between two people, optional escrow, leave feedback, done. No need to trust anyone else's potentially political bias through negative feedback.
I think you have it backwards. the "trusted feedback" is not meant to protect against superfluous negative feedback, it protects against sock-puppet positive feedback gaming the system. I can make a bunch of accounts and give myself rave reviews, but those would all show up as "untrusted feedback" since you have no reason to trust any of those accounts, and thus you would still want to be wary of me.