Thanks @elidy and @elsat, this is indeed handling of unknown event kinds, I added this after @PABLOF7z suggested it in nostr:note16pgkeuxvkl3y8c7zgn9zvnn8w4xwqals9henwag5edez3gx8e9wqm33qep

More clients should implement this, its one of the few ways we leverage the current kind-1 network effect to grow the Other Stuff