another question is if Webmention's WebAPI allows at least 10kb of POST (so far unspecified amount?), it could fit 2000 unicode characters (or 10000 ASCII) message itself, without requiring the message to be published on 3rd server. playing alternative of #nostr relay. Or Nostr relays one day start working with webmentions. meanwhile nostr relays been moving towards self publishing of web pages via decentralized hosting nostr protocol NIP.