PSA: There is apparently a fedi-to-bluesky bridge project that is opt-out by default.
https://ieji.de/@snarfed.org@snarfed.org/111919380001285500
I have opened an issue on github as asked by the original poster @snarfed.org:
https://github.com/snarfed/bridgy-fed/issues/835
Opt-out mechanisms include domain blocking at an instance level or adding yet another hashtag to a profile, which I personally find inadequate and insufficient.