I prefer the first option, and would prefer to be able to opt out of it (longer comment below about what I've got in mind).

For a 'standard' comm, you'd need controls and safety precautions, but for someone like me looking for an outward facing comm, the whole point of interoperability as a project is to allow people to just get on with it.

I really want Twitter commenting here, I really want an easy taskflow for identity login, and I really want comms to be able to let people post with whatever they're logged in as.

Spam is always a concern, but if it's in some way moderated, that should solve it--maybe ID accounts can only post unmoderated to paid comms?