To illustrate even more: I follow a Lemmy privacy “group” with an Akkoma account.

AFAIK its “by design” meaning an inherent property of the fediverse.

If I dont follow someone or my instance isnt federated with those of other followers we cant see each others comments or likes etc

The big deal is I help others make money of me without my consent or getting something back in return. At least not usefull to me. On top of that they track the hell out of me with surveillance.

That would require blocking their servers/domains/IP adresses at the firewall level I guess? Preferably taken from a curated list like NextDNS does?

They correlate the content of your posts with all the other data they have about you, taken from every app (besides WhatsApp, FB etc) that has FB trackers built in. Then that aggregated profile will be used with AdTech to serve ads and make money. I personally object to Meta making money with my personal data without me using their products.