> Now, living in a bubble is trivial. It's also the subtle default on a lot of social platforms.

Indeed. IMO, social media should have very limited facilities for blocking/muting (e.g., maximum number of accounts to block, no blocking accounts that have never previously interacted with you, and no import functionality), so that it could only be used to stop true harassment, and not to intentionally live in such a bubble. That's one of my biggest criticisms of Bluesky: the whole design of their blocklist system seems to be to intentionally encourage this sort of thing.