Trust goes down when you click, so an outside auto clicker will keep it at zero.. it shouldn't hurt your signal velocity much. Trust and Obscurity get averaged to arrive at a final multiplier. And the value is clamped so it can't zero out your score. At higher levels it's much easier to keep both stats higher, leading to better signal velocity. I don't use an external autoclicker so I never tested it that way, I probably should have.