OK, I didn't see where to add my username before posting. But changing it doesn't seem to have changed it for the post already made.
Discussion
Maybe have a pre-send prompt for first post for anyone who hasn't personalised their profile already (that they can ignore if they want)?
Ok, it just updated for me! It is a bit unreliable, it's a known bug I am working on. NOSTR can take a minute or two to propagate the profile changes, I'll note that in larger font.