Doesn't work yet, but are close

app/controllers/forumthreads_controller.rb

@@ -10,6 +10,7 @@ class ForumthreadsController < ApplicationController
     @threads = Forumthread.filter(current_user, params[:title].try(:slice, 0..255), params[:content].try(:slice, 0..255), params[:reply].try(:slice, 0..255), params[:label], User.find_by(ign: params[:author].to_s.strip) || params[:author], params[:query].try(:slice, 0..255), Forum.find_by(id: params[:forum]))
     .page(params[:page]).per(30)
   end
+
   def show
     if params[:reverse] == "true"
       @replies = @thread.replies.order(id: :desc).page(params[:page])

app/views/forums/edit.html.erb

@@ -25,6 +25,10 @@
       <td><%= f.label :necro_length, "Necropost warning delay (in days)" %></td>
       <td><%= f.number_field :necro_length, placeholder: "Warning Delay (leave blank for no warning)" %></td>
     </tr>
+    <tr>
+      <td><%= f.label :disable_deletion, "Disable deletion of threads for non-staff" %></td>
+      <td><%= f.check_box :disable_deletion %></td>
+    </tr>
   </table>
   <p><%= f.submit "Update Forum", class: "btn blue left" %></p>
 <% end %>

app/views/forums/new.html.erb

@@ -25,6 +25,10 @@
       <td><%= f.label :necro_length, "Necropost warning delay (in days)" %></td>
       <td><%= f.number_field :necro_length, placeholder: "Warning Delay (leave blank for no warning)" %></td>
     </tr>
+    <tr>
+      <td><%= f.label :disable_deletion %></td>
+      <td><%= f.check_box :disable_deletion %></td>
+    </tr>
   </table>
   <%= f.hidden_field :forumgroup_id %>
   <p><%= f.submit "Create Forum", class: "btn blue left" %></p>

app/views/forumthreads/edit.html.erb

@@ -11,6 +11,8 @@
   end
 %>
 
+<% forum = Forum.find(@thread.forum_id) %>
+
 <h1>Edit Thread</h1>
 <%= link_to @thread.forum.group, forumgroup_path(@thread.forum.group) %> → <%= link_to @thread.forum, @thread.forum %> → <%= link_to @thread, @thread %> → Edit thread
 <%= form_for @thread do |f|%>
@@ -37,5 +39,7 @@
   <%= render partial: "md_editor", locals: {name: "forumthread[content]", content: @thread.content} %>
   <p><%= f.submit "Update Thread", class: "btn blue left" %></p>
 <% end %>
-<%= button_to "Delete Thread", @thread, :method => "delete", data: {confirm: "Delete thread & comments forever?"}, class: "btn red right" %>
+<% if mod? || !forum.disable_deletion %>
+  <%= button_to "Delete Thread", @thread, :method => "delete", data: {confirm: "Delete thread & comments forever?"}, class: "btn red right" %>
+<% end %>
 <div class="clear"></div>