Simple as that. You go to /settings ---> Display ---> Disable notifications.
All duel-relevant chat messages, as well as invites are no longer shown.
I agree, if the duel limit doesn't get added this should, if alot of people are dueling eachother it gets spammy and annoying.
I'd even say reset the messages/notifications to only be shown to the respective players (and maybe to players around them, so it's not too confusing when they pop out of existence)
No one really needs to hear who's dueling who. But yeah, this is a good compromise in my view.