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/show.html.erb

@@ -9,7 +9,7 @@
 <% @topic_view.posts.each do |post| %>
   <% if post.user %>
     <div class='creator'>
-      <b><%= post.user.username_lower %></b>
+      <b><%= post.user.username %></b>
        <%= "(#{post.user.name})" if SiteSetting.display_name_on_posts %> —
        <%= post.created_at.to_formatted_s(:iso8601) %> —
        #<%= post.post_number %>