I wrote a note about this last week:
A piece of OpSec advice for #nostrplebs:
#Nostr is fantastic and wonderful, but its resilience against censorship comes with inevitable trade-offs: 
Nostr is entirely public and open.

Every single event you broadcast to the relays can be consumed by anyone in the world, and this doesn't just include the notes. 

For example, I can know with whom you've exchanged DMs and at what time (though the content of the messages remains encrypted).

I'm not saying that #nostrices should hide who they are and what they think, quite the opposite!
Just be cautious not to reveal personal information that could get you into trouble.