Hi, I got this annoying problem.
After saving from the front End Editor, all P tags are stripped out from the code, which of course kills my layout.
For your info, I got this in functions.php:
// remove auto p
remove_filter('the_content', 'wpautop');
// remove auto formatting
remove_filter('the_content', 'wptexturize');
remove_filter('the_excerpt', 'wptexturize');
But even when I delete them, I still got the same issue.