Doing some reading about how this should work in the context of XEP-0045 ( )

An implementation MAY allow an unaffiliated user (in a moderated room, normally a participant) to register with a room; as a result, the user will become a member of the room and will have their preferred nickname reserved in the room.

This would suggest that an affiliated user might not be able to register? Is this a XEP problem?

If the desired room nickname is already reserved for that room, the room MUST return a <conflict/> error to the user

This sounds like we’re not returning the correct error message

If the user did not include a valid data form, the room MUST return a <bad-request/> error to the user

This sounds better (if the operation is indeed not allowed)

After the user submits the form, the service … MAY immediately add the user to the member list by changing the user's affiliation from "none" to "member"

We’re not at “none”, and it’s only a MAY. Maybe we can register an affiliated user and still be compliant, just with a check of a bare JID’s affiliation with the room, and skipping any affiliation change if one exists? We’d still need to send a positive result to the user, but probably no presence info would be required to the other users, unless a nick change also occurred AND the nicks are enforced.