If you attempt to italicize text in a story submission using <i></i>, when the submission actually appears in the firehose instead of italicized in-line text, the marked up text will actually appear on a new line, indented akin to a quotation.
What is worse is that when you preview a submission the preview appears italicized so you can't actually tell if <i> tags will work when you later submit, and the quotation effect does not occur in the preview display, so there is no way to know your submission will look broken later, except by learned experience.