Which mobile app? I don't think HN have an official app, and I'd like to know if one of the 3rd party apps needs a hand with any issues. Not sure if I could help, but I do like hunting down random bugs :-)
I don't recall exactly how it happend but I think I was reading an article, then went back to the home screen and selected add comment from the dropdown of that article row. It may have also been user error.
