In 6.1, it says "Hubs MUST ignore verify mode keywords that they do not understand." This is good, but I suspect that the protocol would benefit by extending this. Whenever you have one of the requests and there's a field in it you don't understand, hubs and subscribers MUST ignore. Might want to steal the language from http://atompub.org/rfc4287.html#extending_atom
This buys you all sorts of room for organic growth & versioning down the road, people can put in new fields without breaking old clients. -T
