Removing this option with no substitute is unfortunate. Some browsers will adjust the number format based on the browser locale (i.e. Chrome will automatically use a comma in client-side validation but then send a period as the decimal character in POST). I suppose if other browsers follow suit that may make some kind of consistency.

Original Drupal discussion is at https://drupal.org/node/1519852, but didn't really touch on the usefulness of this option.