Lists can be set off, as above. Words can be emphasized , headlines made to stand out , and literal text marked appropriately. Plain text also cannot adequately capture the structure of a document, e.g. the section break that appears a few paragraphs below. The rapid growth of the World Wide Web brings the problem into sharp focus. One answer is text.
Writers can write, using any software on any computer.
Text databases can be a source or result. But plain text is not a good answer, it's simply inadequate. Having writers learn HTML markup is also not a good answer. We need something new. However, as discussed below , I think it is not an adequate solution.