Standardize links to wiki help pages.

* Fix inconsistencies in how wiki pages were linked.

* Link directly to the wiki instead of to a title search that is expected
  to redirect to the wiki.

app/views/comments/_index_by_post.html.erb

@@ -1,7 +1,7 @@
 <div id="p-index-by-post">
   <% if !CurrentUser.user.is_builder? %>
     <div style="margin-bottom: 1em;">
-      <h2>Before commenting, read the <%= link_to "how to comment guide", wiki_pages_path(:search => {:title => "howto:comment"}) %>.</h2>
+      <h2>Before commenting, read the <%= link_to_wiki "how to comment guide", "howto:comment" %>.</h2>
     </div>
   <% end %>