User blog comment:Dragonjet/Ban Safety/@comment-128.199.254.26-20160115045206/@comment-26091666-20160115070900

Most likely they will trace it back to your account and ban your account rather than banning both you and your friend's account via IP address.

No, it is complicated in how they work. Devs means Kadokawa or the individual game developers behind the games hosted on DMM. If you get banned from one game, say for instance KanColle, you can still play other games hosted on DMM and not KanColle. I am certain DMM is only responsible for hosting the game content (and most probably for a fee) but leave the individual bans up to the publishers themselves.