That's a people problem though, not a technology one. Surely you can resolve this by talking to the person, then their manager? If it still doesn't resolve it

That's a people problem though, not a technology one. Surely you can resolve this by talking to the person, then their manager? If it still doesn't resolve it, mute them and advise you've done so due to abuse of notifications, and their issues will always be looked at when you're next looking.