UX: Improve username readability in search results

Avoid lower-case usernames in search results output to improve readability and accuracy - avoid users reading words that don't exist.

app/views/topics/plain.html.erb

@@ -11,7 +11,7 @@
 <% @topic_view.posts.each do |post| %>
   <% if post.user %>
     <div class='creator'>
-      <b><%= post.user.username_lower %></b> <%= "(#{post.user.name})" if SiteSetting.display_name_on_posts %> at <%= post.created_at.to_formatted_s(:long_ordinal) %> — #<%= post.post_number %>
+      <b><%= post.user.username %></b> <%= "(#{post.user.name})" if SiteSetting.display_name_on_posts %> at <%= post.created_at.to_formatted_s(:long_ordinal) %> — #<%= post.post_number %>
     </div>
     <div class='post'>
       <% if post.hidden %>