WoT can be in the client or it can also be on a relay. Like my relay nostr.mom uses WoT for comparing reports of users with their trust score in order to slow down a user or not. To check whether reports are authentic or whether there are enough reports that are enough to slow down a user. WoT can be also useful for determining whether a fresh user has enough score to be able to tag many people, add a lot of images, send a lot of links or not just in the beginning of his adventure.

My relays actually require PoW sometimes. I guess I am the first users of dynamic PoW. Based on how much a user spams my scripts sometimes require more PoW before dropping the user altogheter. So these requirements act like a warning if the user happens to listen to relay responses.

I think some relays will get better at handling spam and thats a good thing. A gradient of options is good for nostr users.