At some point meta tried purchasing anonymized patient data from hospitals.

We are also discovering there are many subtle way to identify a person, like grammar, spelling speech patterns (tor specifically warns against this).

Chances are high they already have some data on you, all they need is enough subtle unique things in your data to rule out anyone else. Based on the times your most active and references you might make.

Now i am not a zuck owned superai but to give you my human attempt for an initial culling:

A social security number is the name of the American name of such number. Purposely sounding American is a strategy on itself for non Americans but the act of trying to hide your identity by pretending to be from the us can be an identifier as-well. You also seem to be more on the political left so your your likely part one of 160 mil people (for convenience i am assuming a 50% split in left/right ideology in the us)

In most countries your isp have some of your personal details your isp is also able to see all the internet domains you visit. They cant see what you do on them but because every instance has its own domain they have a timestamped list of all federated instances you visit.

It only takes that info to be leaked/hacked or sold for the big corps to obtain it. Of course if you use a vpn your isp cant see the domain but if you do have a vpn congratulations cause its yet another identifier and they too can be hacked or be selling this data.

The best way and only (still not guaranteed) way to remain anonymous is by using tor browser in windowed mode. Refraining from interacting and if you post to run your speech trough an ai algorithm to generalize/neutralize any personality from it.