Purpose:
Allow for users to vote on a post at any point while reading a post.
Justification:
If I'm reading a post that I really like, I can know within a few paragraphs or less that I'm going to vote for it. I'd rather vote without scrolling down to the bottom and losing my place.
Design:
Just a simple little transparent frame that sticks to the bottom right/left corner of the page UI which allows for upvotes and/or shares of the post.