Earlier quoted context omitted.
As an Opera user I find it a bit annoying as well but I think it's just a silly warning that doesn't impact functionality.
it did for a while when we used the canvas I believe, we had some major issues - but there was one charting thing that just needed it and we couldn't get it to work on IE/Opera... so we tried to fix it, but got stuck.
1. Open your app in Opera (if there's a hard link to a page containing the offending issue then it's even better) and go to the main menu button - help - report a site problem, and you should fill all the relevant details. Hopefully you will get someone from Opera to assist you since they have an entire team dedicated to this sort of thing.
2. You can check the answers to this post (Opera IamA on reddit, 1 year ago)
http://www.reddit.com/r/IAmA/comments/dtbcz/hey_reddit_join_...
and you can try sending the Opera employees PM-s with your problem. I'm sure it will be sorted out in the end.
Cheers.