If you upvote me, then I learn that you like or agree with the specific ideas I've articulated in my writing. If I write "blue is the best color," and you agreevote, then I learn you also agree that the best color is blue.
But if you disagree, I only learn that you think blue is not the best color. Maybe you think red, orange, green or black is the best color. Maybe you don't think there is a best color. Maybe you think blue is only the second-best color, or maybe you think it's the worst color.