> Why can't I collapse comments

Features like this could easily be a declarative feature in HTML. e.g. something like:

    <div class="comment_wrapper">
        <action type="show,hide" for="foo">
          <img ...> <!-- or whatever -->
        </action>
        <div id="foo" class="comment"> ... </div>
    </div>

Unfortunately, development of new HTML features like this mostly stopped when a major browser developer decided to try to fight with Microsoft for the desktop/mobile markets by changing webpages into software.