I have just discovered something new about the reputations system. I recently neg-repped somebody for the first time. (It was for very bad behavior, and it was signed.) After doing so, in order to not run into problems because I forgot my rep was set to negative, I decide to give positive rep to a post I'd been meaning to give rep to anyway. When I went to do so,
my box had been automatically reset to positive. I don't know if this was just a fluke or what, but hopefully it will help eliminate accidental neg-reps in the future. Just wanted to let you know!