One idea to consider. Make it easier to implement by changing the query syntax. Instead of a query parameter, which always requires a script to process: examp

One idea to consider. Make it easier to implement by changing the query syntax. Instead of a query parameter, which always requires a script to process: example.com/.well-known/avatar?resource=acct:username@example.com Make the requested email address part of the path: example.com/.well-known/avatar/username@example.com People can put images into their HTTP server directory named as email addresses. This makes it easier to implement for vanity domains. No server-side code necessary. It still allows someone to build a dynamic script that handles the "/.well-known/avatar/" path.