I have gotten banned for Playing Pokemon Moon.
I have a NNID Associated with my 3DS, I have never played Pokemon Sun or Moon online at all.
I have accessed the Friend Plaza, but it was always on local wireless and never online at all.
If I was prompted if I wanted to connect to the internet, I always declined.
Just having your 3DS's Wi-Fi on is enough.
Even if your system had it installed, if there's any trace of it left and your 3DS has connected to the internet, you are boned.
I contacted Nintendo and gave them the two error codes, and according to the specialist I was transferred to, it's a permanent ban.
I do not know if you can still get banned if you play when the game comes out, but they did state "any unauthorized game code" which would imply any .CIAs that are installed on your system that your account history on the e-Shop doesn't show.
The latest firmware must have some sort of snooper that cross-references every installed title ID on your system with your console's e-shop account, and if there's any mis-match, you are B&'d
This is a BAN WAVE, that means the bans are being sent out in waves. So if you are not B&'d now, you will most likely be B&'d in the near future. If you never get B&'d, go play your local lotto as you are lucky!