Currently, linebreaks or enters are not allowed in metadata textboxes. In the usecase of Description or Abstract, it's often the case that the text contains paragraphs. Including these paragraphs will increase readability for the end users. Furthermore, not being able to hit enter in a paragraph textbox (not talking about text fields) is not the expected behaviour of such a field.
Its my understanding that the current behaviour is by design, and not identified as a bug. I do hope that these arguments will allow a re-consideration.