Bluesky: interpret "logged out visibility" as opting out

[snarfed]

We're not currently looking at Bluesky's "logged out visibility" profile setting, but we should! If it's off, we should interpret that as meaning the profile isn't public, and we shouldn't backfeed any of its responses.

Background: https://bsky.app/profile/hilarybaumann.com/post/3lbaivloiwc2r