It's a known bug that EA hasn't gotten around to fixing yet. Most people have this issue. You can temporarily make the chat box go away by pressing the ~ key, but there's not a permanent fix for this yet.
Thank you SIR !
I just wanted to confirm that this was a known issue, the flickering is driving me crazy especially when you are sniping and the box appears right at that moment. I tried pressing the ~ button but that box appears more than 500 times each round so there is no point.
Hopefully we can get a patch soon that fixes this issue, it shouldn't be that hard to fix