Oh wow, I've been granted Karma Power. I appreciate being entrusted with the capacity to assess the posts of other folks on the board. As a former college teacher, I've assessed students of varying points of view and from all backgrounds and I will be exceedingly fair. I'll assign a minus for the rare, nasty cases where someone is spamming, threatening, or being insulting on purpose, etc. (basically for what others have said they will assign minuses for). Likewise, a plus will go to anyone who contributes something positive or useful to the forum and not because I may agree with them.
I was never a hard grader, but I wasn't an easy one either - I have to be impressed or thoroughly repulsed for the A or F, respectively.