I shared this (somewhat old) post hoping old HN discussions would auto-pop-up but it looks like it wasn't discussed much at the time. I was hoping to find some elucidation of _what_ Webfinger is doing here and/or when it's actually invoked by Mastodon federation. The Webfinger document we create in this tutorial is never served up or posted anywhere. So mastodon doesn't need it for you to reply to a post. When does it come into play?