@dang, if you're listening, an idea:

make the "upvote" buttons invisible on stories that the user hasn't visited before. This could be done like so:

    // css
    a.upvote-botton:visited { visibility: hidden };


    <!-- in html -->
    <a href="{article_link}" onclick="perform_upvote()" class="upvote-button">upvote triangle</a>

The href & onclick handlers would need to be added in javascript so as not to affect hn for non-js users.