I am not sure this is a bug or plain IE11 issue. But, when I post a forum in latest version of Moodle (2.6.2+), the page shows "Required" message even though there is something in the message box. See attached image. Then, I have to hit the post to forum button again and it will go through.
This is not just the forum posting. Anytime something needs to have message, this issue happens.
It does not seem to happen to other browser, IE 10, Firefox, and Chrome.