comments: adjust link to howto:comment.

Replace the giant banner about reading the comment guidelines with a
smaller link to howto:comment beneath the comment text box.

app/helpers/application_helper.rb

@@ -227,6 +227,7 @@ module ApplicationHelper
     options[:value] ||= instance_variable_get("@#{object}").try(name)
     options[:preview_id] ||= "dtext-preview"
     options[:classes] ||= ""
+    options[:hint] ||= ""
     options[:type] ||= "text"
 
     render "dtext/form", options