"An estate owner can't suspend an account for ToS violations, either, right?"

Exactly.
As an estate owner, I have no more power than ANY other land-owner. Notecard spamming is notorious - I hate it. Fortunately I don't receive it often enough for it to be that much of a bother.

And that's handled through profiles, so it doesn't matter if they're banned from your parcel or estate or whatever. Supposedly, Linden Lab will get copies of abuse reports that are directed toward estate owners.

As for 'powers' of discipline - I can see where banning would help. For instance - someone comes to the store of one of my tenants and drops landmarks to their competing store on all the people there. I can ban them from the estate and they can't even TP to the island. Of course, they can just go and make another account (But I don't allow anyone younger than 7-days to stay - they automatically are TP's home for this reason.)

Unless, of course, as an estate owner who receives a more serious SR - I (estate owners / concierge customers) carry any more weight - or are taken more seriously if we bring that particulat AR to LL?

I really don't know.

All I was saying is that I would take the report seriously, and actually investigate it. Not swipe the hand of 'discipline' in a wide swath without thinking about it. And I would report in detail my findings to both (or all) parties.