Remove if_user and similar methods

Rather than hiding features based on CSS, just avoid including them
in the output. Fixes #1862

test/integration/user_changeset_comments_test.rb

@@ -12,7 +12,9 @@ class UserChangesetCommentsTest < ActionDispatch::IntegrationTest
       assert_select "div#sidebar" do
         assert_select "div#sidebar_content" do
           assert_select "div.browse-section" do
-            assert_select "div.notice.hide_if_logged_in"
+            assert_select "div.notice" do
+              assert_select "a[href='/login?referer=%2Fchangeset%2F#{changeset.id}']", :text => I18n.t("browse.changeset.join_discussion"), :count => 1
+            end
           end
         end
       end