When user enter content to html editor specilaly in case of  "copy&paste" action they may by mastake enter attribiute like id that exist in moodle page an can make to HTML/Javascript error. real senrio case stady was in essay question in quize when some of the student try to copy previues multi answer question and paste it in the same page in atto editor, this action couse to empty answers on the questions.

If the HTML editor will filters filed id that already exist or generated by Moodle it's can help and avoid such UX issues.