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.