Obviously with WordPress, I write an individual post and the software does everything else. So I’m prepared to struggle with the code in an individual post — using an unfamiliar language, the way I did in freshman Russian. What escapes me is which little bit is suddenly italicizing the text in every subsequent post on the page. It seems as if I shouldn’t be able to wreck the whole page…
If you have an unclosed ‘‘ or ‘‘ tag in your post, that will have the effect you described.
…and the bits the system ate were meant to be <em> and <i>.