I came here to report the same. Seems it hasn’t been fixed or it has regressed?
I’m trying out a goal where I was planning to extensively use ampersands in the comments, so hopefully it’s an easy fix! Thanks for looking into it.
See also Dashboard shows special character ampersand escaped
ETA: To be clear, I only see the escaped ampersand on Beeminder and on the goal detail page in the iOS app. On the website’s goal detail page, the ampersand shows up as it should.