I noticed that this wasn't actually mentioned...

As some of you have mentioned, you can indeed go over 9999 damage limit. You just don't see it in battle. You can find out what is the highest that you've dealt by talking to the old guy in the hidden room of tavern in Gyshal or however that's spelt (the town that's blocked off and must be reached by ship[airship or plain ship] on the floating continent). I was level 30 ish and my Scholar scored me a 13K max damage via item, now I'm gonna train my Black belt to raise that number even more