The Text Area field type does not support multi-line placeholder content, including line breaks. Suggest the placeholder field be a textarea just like the default field.
Text areas, from the information I can find, do not support multiline placeholder text http://w3c.github.io/html/sec-forms.html#the-placeholder-attribute. The only thing I can find information on are hacks and work-a-rounds that may not work in all browsers http://stackoverflow.com/questions/7189223/can-you-have-multiline-html5-placeholder-text-in-a-textarea.
Since this is the case, I wouldn’t consider this a “bug”. Granted, I’m not the developer, so I can’t say he wouldn’t figure out how to do it, but since it’s not something the HTML specification allows or is supported by all browsers….