I like it. I think it will have to be implemented carefully. And I do 
believe to do this properly you have to do this at the relay level. 
Simply hiding content from users feeds in some clients doesn't solve 
your mention of "personal safety" in terms of privacy. Also as a piece 
of client software I expect users to have full control of these features
 and I personally will have it disabled all the time if I could, I think
 many other users would too. If I can get the note from a relay I want 
to see it.