for the down vote, then would that mean the rules would need to be changed again to allow "disagreeing with a post" as an acceptable reason to down vote? Since I believe the whole reason for the voting was to provide a way for the forum to police itself, then I would think adding "disagreeing with a post" may infringe or at least blur the policing function.

I do agree with you that it would be nice if people did provide an explanation for why they downvoted a post because I do think some of the downvotes are as a result of disagreeing with the post. However, posters could get around it by simply typing "disagree" and I am not sure posters want to see the same post repeated by potentially every downvoter because of the space it would take up within the thread. Unfortunately, I am not sure there is an easy fix without Will and/or Chris spending all their time policing the boards (something they don't want to do or should have to do). Even though there are rules/guidelines in place on how the votes should be used, it doesn't mean posters will always follow them. If that were true, then there would be no crimes committed in this world.