I'm pretty sure the intent when upvotes and downvotes were created was to use them in regards to relevance. Is the topic about ducks and someone is going off about jeeps? Downvote. Is the community about posting DIY peanut butter but someone keeps posting Skippy™? Downvote.
It shouldn't have anything to do with agreeing, effort, or anything like that. Just a way to keep the topic/community on track.
This is silly though, isn't it? Most people think most things that they disagree with are low quality by nature of being something they disagree with.
Whatever was intended for them, IMO upvotes and downvotes work because everyone just uses them however they want, and the sum total of everyone doing that averages out to a somewhat passable quality sorting system. Trying to tell people how to use their upvotes and downvotes is just yelling into the wind.
I'm kinda glad we downvote the things we disagree with. Whether on topic or not, shit opinions don't deserve to be displayed with the same prominence as reasonable opinions.
And that's how a community become an echo chamber. Also assuming any opinion you agree with is reasonable and those you disagree with is shitty is silly...