= f.autocomplete_field :tag_names, autocomplete_tag_name_ideas_path,
   'data-delimiter' => ',', :multiple => true,
   :placeholder => EXAMPLE_TAGS, :class => "input-text big"

= f.autocomplete_field :tag_names, autocomplete_tag_name_ideas_path,
   'data-delimiter' => ', ', :multiple => true,
   :placeholder => EXAMPLE_TAGS, :class => "input-text big"

Add space to tag editor delimeter
Add space to tag editor delimeter

For readability, separate tags by an additional space, not just the
comma character.
