User blog comment:Dopp/Technical Update: October 4, 2011/@comment-3134619-20111007022912/@comment-4126310-20111007031853

Yes. I noticed this yesterday. If you're sure you didn't make any mistakes (and when undoing an edit, how could you?), you can go ahead and press "Publish"; it should leave the markup intact, no matter what the preview window says. Since this bug was introduced, however, I always check the History and compare my revision with the previous one, just to make sure that I really only changed what I wanted to change.