@Gargron Great!

I advise it to make it opt-in by default and make the opt-out/opt-in question configurable for server admins in config/setting.yml. I also would make bots always opt-out.

I also have a related idea about account presets. That people can choose at sign-up (or later if they want) what kind of account they want with associated settings. The account preset 'journalism and media' would e.g. enable QT's, enable discoverable, enable search indexing, etc. On the other site will the account preset 'as private as possible' enable all privacy features, post visibility to followers only, lock account, etc. Just an idea that popped out in my head. Maybe I need make it a Github issue.