SHOULD update its copy of the object of the same id to the copy supplied in the Update activity. Unlike the client to server handling of the Update activity, this is not a partial update but a complete replacement of the object.

Where the "of the same id" refers to having the same id as the object referred to in the update action. It seems like Updates are underspec'd in activitystreams and activitypub carries that forward - to me it seems like an Update should always have a origin that is the id of the thing to be updated (rather than it being inside the object, which is a weird mixture of data and metadata), and then since changing an id is a special case that should be handled by including a target. That fits the semantic definition of the terms: "Update from (origin) {x} to (target) {y}"

@jonny Last I heard, Mastodon uses AP IDs to identify and deduplicate accounts in most places, but requires that "username+server" tuples don't change either, as more of a tech debt thing than a schema decision. I think there's a GitHub issue somewhere about rectifying this.

Did you see this little @canary project of mine? https://correct.webfinger-canary.fietkau.software I made a whole thing about what AP servers need to do to support dynamic handles (mutable usernames and domains). It's closer than you'd think.

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However, I've just re-read the original article (https://www.w3.org/Provider/Style/URI), and… hm. This is not nuanced enough. The rest of Tim BL's 1998 style guide is outdated, wrong, or overly-simplistic, but my sentimental attachment to this particular article was preventing me from seeing its flaws.

Do you know of a better canonical reference for how URIs should work?

basically what i'm asking here is if anyone has actually tried this (and ideally succeeded) or if we are just gonna have to do this on our own. surely we will not be the first to try and it seems like someone must have written down their experience somewhere...