Only actually public, i.e. not "unlisted". One exception: Share
an update if the update changed the visibility from "public" to
something else. The fasp can act on this information then.
Only share statuses where the account has `#indexable` set
to `true`.
Only share accounts where `#discoverable` is set to `true`, with
one exception: If `#discoverable` has just been set to `false`
this is an important information for the fasp.
