I've often thought of making a web site with two voting mechanisms. Here's a million dollar idea you can have for free.

The two voting buttons on every post are:

Agree vs. Disagree

Important vs. Not important

Disagree/Important means that even though I disagree with this comment, it makes an important point, and I recommend others should read it.

Agree/Unimportant means that even though I agree with this comment, it doesn't add anything significant to the conversation, and you can safely skip reading it.

Any web site with only one voting mechanism will surely have different people with different opinions on what that one voting mechanism means.