They can't. That's the point. :)
Discussion
That’s how you keep the boomers out
Boomers as well as anyone you don't want to know who you are .. privacy in open ..
This is a wonderful idea - as a facebook or email replacement ..
Unlike Twitter , on Facebook we want only close family and friends to follow us .. we can share our xpub with them .. for the rest, our notes would be anonymous..
On email - a message may be open to everyone.. but the identity is associated only by those who got xpub ..
At client level - users may toggle between notes from known people ( xpub) or anonymous notes -
Anonymous notes can be bold free speech ( without fear or persecution) - but still limited by reputation of their xpubs .. which is a good thing ..