Redmine

search results display closed issues with a regular style. It would be great if those issues that are closed would also have the class "closed" to make ability to be styled with line-through.

It could be done by adding following into the existing code (it is as I have implemented in my own instance):

+++ app/views/search/index.rhtml        (working copy)
@@ -26,7 +26,7 @@
     <h3><%= l(:label_result_plural) %> (<%= @results_by_type.values.sum %>)</h3>
     <dl id="search-results">
       <% @results.each do |e| %>
-        <dt class="<%= e.event_type %>"><%= content_tag('span', h(e.project), :class => 'project') unless @project == e.project %> <%= link_to highlight_tokens(truncate(e.event_title, 255), @tokens), e.event_url %></dt>
+        <dt class="<%= e.event_type %> <%= 'closed' if e.event_type.eql?('issue') && e.closed? %>"><%= content_tag('span', h(e.project), :class => 'project') unless @project == e.project %> <%= link_to highlight_tokens(truncate(e.event_title, 255), @tokens), e.event_url %></dt>
         <dd><span class="description"><%= highlight_tokens(e.event_description, @tokens) %></span>
         <span class="author"><%= format_time(e.event_datetime) %></span></dd>
       <% end %>

also .css should contain the proper style. I have following below:
dt.closed a { text-decoration: line-through; }