By the way, i did both (i have a wot relay, a have a relay where i filtered out the spammers, and a i have a relay where i enforce NIP13 difficulty). I can choose what i want to see at any time by just switching relays. pretty cool, huh? 

 How does that work? The nip13 relay I mean? What’s considered proof of work to be able to write 

 Just like the NIP13 says: you need to "mine" an id for the note that starts with as many zeroes as the difficulty you set. In the relay i just check if the number of zeros matches the mined difficulty.