What about giving different weight to trust feedback? I can think of 2 ways of doing it. One would be by trust depth so depth 1's weight is 1, depth 2's is 0.75, and even depth 3's could be 0.5 or something like that, the other option is encouraging users to set their own trust list by weighting 1 one's own list and 0.5 the default trust if included. An account would be red if it received at least 1-weight of negative trust so a single feedback from someone on depth 2 or depth 3 wouldn't be enough but would still appear as trusted feedback.
That does seems like a wonderfully creative idea for weighting the top of default trust.
Full disclosure, I've now become trolled by Quickseller in what seems to be be just the kind of potential abuse that I was suggesting that this would clear up. To be clear, this was
not the case when I started this thread. I now have quite a vested interest in this issue (I've now been abusively negrepped by a person with whom I've had no business or trades) whereas it used to be more "academic".