Change the way nuked users' posts are handled. Allow null in the user_id column of posts. Show these posts in the posts stream.

spec/serializers/post_serializer_spec.rb

@@ -0,0 +1,25 @@
+require 'spec_helper'
+
+describe PostSerializer do
+
+  context "a post by a nuked user" do
+    let!(:post) { Fabricate(:post, user: Fabricate(:user), deleted_at: Time.zone.now) }
+
+    before do
+      post.user_id = nil
+      post.save!
+    end
+
+    subject { PostSerializer.new(post, scope: Guardian.new(Fabricate(:admin)), root: false).as_json }
+
+    it "serializes correctly" do
+      [:name, :username, :display_username, :avatar_template].each do |attr|
+        subject[attr].should be_nil
+      end
+      [:moderator?, :staff?, :yours, :user_title, :trust_level].each do |attr|
+        subject[attr].should be_false
+      end
+    end
+  end
+
+end