I disagree, as noted further up the thread. Preventing downvotes doesn't remove the dissenting opinion. In fact, it allows and encourages it. Downvotes allow groupthink to silence disagreement. If you disagree with something, instead of downvoting, post a comment explaining your position.

Likewise if you agree with something--then posts can just be sorted by comment count. Of course, it could be said that the upvote button is just a collapsed and made-convenient form of replying "Me too!"

Wouldn't it be interesting, then, if instead of editing a metadatum, clicking the arrow made a duplicate of the post (or, rather, a Post object with the votee as its prototype), which then stacked under the original...

"'A stacked comment' posted by bob, joe, fred"

So what happens if something stupid or banal gets voted up to the front page. What if it's something that I don't think is relevant or useful.

Should I upvote every other article to express my opinion? :)

People who agree with an article/think it's important/useful have an immediate way to express that in a useful way - an upvote.

You don't have the same capability if you strongly disagree with an article, see it as unimportant, not relevant, or off-topic. I still think that's a shame.

An alternative would be using flags, like reddit's 'report', the idea being you only use them for stuff that is really unsuitable, like spam, trolls and stupid stuff.

That's not a bad idea.