I'm sorry, but I have to strongly disagree with you. Delete requests honoring can't be enforced on the protocol level. And the idea that it can be done and users could rely on it is dangerous. 

For relay to be compliant with the protocol (now or in the future) is enough to not return deleted notes, but you can't make sure that there is no copy of the old notes. Maybe they are still in the database with deleted flag, or they are in backups or they were broadcasted to a private relay not accepting kind 5 at all and you can't query it... 

By changing the wording in NIP-09 from SHOULD to MUST you are not going to change the reality. The only thing which happens is that users will get a false hope of security. 

Most of the relays and clients are honoring the delete requests to the extant that you can get rid of typos or accidental likes. This is good enough for me, but I do automatically assume that bad actor can have all my notes and keep them indefinitely. 

You are right about the one key pair being dangerous if leaked and the idea of using child keys for different services and applications is something we should be talking more.  

 How do you make a delete request to relays? 

 Read NIP-09, but in general it is a kind 5 note with tags specifying what should be deleted.  

 I just clicked another button on amethyst and there is the request delete option. I will add nip 09 to my reading list. This is kid in the candy store time again. Thanks for your pointer 

 Amethyst does seem to include more features than any desktop client I've tried. It seems to be the way of the world now. #fedilab, one of the #android #fediverse clients is better than any of the desktops clients. Kind of annoying for those of use who prefer to keyboard and mouse our way through life 😞  

 Tell me about it. My desktop isn't bang up-to-date as it is, so I'm usually on the phone  to check out nostr apps.  

 > For relay to be compliant with the protocol (now or in the future) is enough to not return deleted notes,

Also, they can choose to not be compliant. What is anyone gonna do about that? Be angry and scream "you're not compliant"? 

 Openly non compliant relays are much better than relays pretending to be compliant. You can at least theoretically choose not to use it, but still someone else can broadcast your notes on it. So yeah, in reality the only difference is the deception.