So … I have managed use use my custom domain and make it point to a shared instance, without hacking Mastodon
… and, it kinda works …
I have developed a small python app webfinger-proxy to alias your own domain handles to a shared instance.
I have setup it on my own domain rjo.name.
firstname.lastname@example.org points to
See the response of the Webfinger https://email@example.com
I have managed to follow this account and send it private messages.
I have another account on the same shared instance, and
firstname.lastname@example.org appears as a completely separate remote account though.
I am not sure whether this is only on the UI or if Mastodon now have a duplicate account for this guy …
I would need some help from the developers to figure this out : Is the handle a primary key ? Or is it the URL ?
Can you see any have adverse effects ?
Do you think the physical migration of accounts from one instance to another would still work ?
I will continue my tests with other implementations :
Pleroma, mobile clients, etc …