Nostur let you see from which client a note is posted from and let’s you add the same tag to to your notes.

I don’t know if all the clients support this, though. 

 I'd rather all people not know. If I want to make my own app and keep in stealthy for instance. 

 Hence optional 

 derp 

 I have seen this before.  Some past coworkers used it in their speech... What is this "derp" that you speak of... 

 When I’m feeling dumb haha 

 Yes, there is a client tag for this you can set on events (notes) when broadcasted. How noStrudel displays this:

https://shares.sebastix.dev/Ek6rM25U.png

  

 noStrudel now displays the author's client, sometimes.
 https://image.nostr.build/82a33690270e8ed3bc8d4a8978d04396cd2f2737682076e6ed9c867aa063882e.png 
 

 Lume will also support it in the next update https://files.catbox.moe/lpdsek.png 

 agreed 

 Clients can always lie, but NIP-89 defines a "client" tag that can be added to notes
I added support for it in noStrudel recently