If a student uses < > in their essay question answer in an essay question that is the second or greater essay question displayed on a page, the text between the <> is lost.
Create a quiz with two or more essay questions.
Display the quiz (with more than one question per page).
Take the quiz, enter <anytext> in the first answer and <anytext> in the second answer.
Due to the fix for http://tracker.moodle.org/browse/MDL-6649 the student answers the first question using the HTML editor, this saves fine. The student answers the second question using a plain text field (see 6649). The plain text field cleans out the text between the <>. I've reproduced this in 1.6.5 and in 1.8+
This is probably related to:
and the same fix for lesson essay questions may work, we're investigating.