Let's check in with nip42, AUTH and use Amethyst and theforest.nostr1.com relay as an example.

"nip42 defines a way for clients to authenticate to relays by signing an ephemeral event.

This NIP defines a new message, AUTH, which relays can send when they support authentication and clients can send to relays when they want to authenticate."

I use theforest.nostr1 relay as my top relay to read and write from. I think if you look, many of you use this relay too. 

You may have noticed this note by 
nostr:nprofile1qqsd6ejdteqpvse63ntf7qz6u9yqspp4z7ymt8094urzwm0x2ceaxxgprfmhxue69uhhg6r9vehhyetnwshxummnw3erztnrdakszxmhwden5te0w35x2cmfw3skgetv9ehx7um5wgcjucm0d5dj64vx 

nostr:nevent1qqs93xdw936muekdly8jswelanhcne7jw09dv5zgxq6mhzc5hy6xx0spz3mhxw309akx7cmpd35x7um58g6rsd3e9upzphtxf40yq9jr82xdd8cqtts5szqyx5tcndvaukhsvfmduetr85ceqvzqqqqqqytmjqnu

By using a client that supports nip42, it will Authenticate the npub to the relay if previously whitelisted to write. Amethyst supports nip42. This will allow you to continue to read and write from theforest.nostr1.com

Now here is where the fun part is. Nip42, AUTH, whitelisting and read/write rules allows for the relay to isolate the notes just to that relay. Only other npubs that are AUTH can see the notes. You are basically able to isolate notes to one relay and those allowed to see them.

To do so in Amethyst:
-remove theforest relay from outbox
-remove mutiny relay from outbox
-remove nostr.band from outbox
-add theforest.nostr1.com as a general relay with read and write enabled

Then when posting:
-tap the relay symbol at the center top of the screen
-deselect all relays
-toggle theforest.nostr1 relay on
-tap save
-tap post

Now that note is only sent to the forest relay and not to other relays. So it is possible to have an isolated relay of writers and readers if a single relay is used. This is awesome for teams and groups.

( The moment someone is commenting without isolating their relays the note gets sent to other relays.)

I found you can write to citrine and theforest and the note remains isolated.

You can have noswhere as search

Now get your AUTH on! 

 nostr:nevent1qqs2qwa3vcayuhrdyrj2m7g7ff5lm00xwpgl0e0r773skun4tevk03qpz3mhxw309akx7cmpd35x7um58g6rsd3e9upzpmd5wqn399avtfslyalne52du4xx066ue5sw7rva72d7rp59hvqyqvzqqqqqqys8jems 

 nostr:nevent1qqs2qwa3vcayuhrdyrj2m7g7ff5lm00xwpgl0e0r773skun4tevk03qpz3mhxw309akx7cmpd35x7um58g6rsd3e9upzpmd5wqn399avtfslyalne52du4xx066ue5sw7rva72d7rp59hvqyqvzqqqqqqys8jems 

 nostr:nevent1qqs2qwa3vcayuhrdyrj2m7g7ff5lm00xwpgl0e0r773skun4tevk03qpz3mhxw309akx7cmpd35x7um58g6rsd3e9upzpmd5wqn399avtfslyalne52du4xx066ue5sw7rva72d7rp59hvqyqvzqqqqqqys8jems