Preventing wrongly topic creation in the forums

There is an issue on the forums here on d.o in that posters regularly post threads in incorrect forums. Most of the forums have a thread explaining the purpose of that section of the forum, but posters still regularly post in the incorrect section of the forum.

I'm thinking that part of the problem may be the 'add new topic' link on the forum top page. Users come to the forum with a question, and click this link. In creating their new thread they need to select the forum, and do so with no guidance whatsoever as to what the various forums are for. This of course is likely to leave them unsure as to which forum to choose, and choose the wrong forum.

If this link were removed from the forum top page, users would need to click the link in the various forums. This would increase the likelihood of them reading the forum descriptions on the top page, and/or the forum description thread on the top of the various forum pages.

In doing this, the forum selection taxonomy selector could be hidden altogether, with the forum being automatically selected. As the forum is automatically selected already when choosing a forum, this would be as simple as implementing hook_form_alter:

function hook_form_alter(&$form, &$form_state, $form_id)
{
  // we only want to hide the selector if creating a thread, we want to leave it when editing
  // a thread in case the user has posted in the wrong section and needs to move the thread
  if(form_id == 'forum_node_form' && !isset($form['#node']->nid) || !$form['#node']->nid)
  {
    $form['forum']['#type'] = 'value';
  }
}

Please note that the above was written off the top of my head, I haven't actually checked the form.