User setting: "Hide" nodes with rep < -1-$NORM/2.

Currently, the only places we "hide" nodes are Newest Nodes, Recently Active Threads, and Search Results. Those would be fine, but hiding replies seems more to the point.

I'm against labeling nodes based on reputation (except numerically). But I don't currently foresee many problems from adding the feature I described. I don't see a pressing need for it either.