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"