You may not have been anonymous to the people in your immediate community, but you were largely anonymous to the people outside of it, which is something that has been systematically dismantled in various ways through history. Even things as basic as last names are there to make you visible to outsiders.

From Seeing Like a State, p59:

The invention of permanent, inherited patronyms was, after the administrative simplification of nature (for example, the forest) and space (for example, land tenure), the last step in establishing the necessary preconditions of modern statecraft. In almost every case it was a state project, designed to allow officials to identify, unambiguously, the majority of its citizens. When successful, it went far to create a legible people. 38 Tax and tithe rolls, property rolls, conscription lists, censuses, and property deeds recognized in law were inconceivable without some means of fixing an individual’s identity and linking him or her to a kin group. Campaigns to assign permanent patronyms have typically taken place, as one might expect, in the context of a state’s exertions to put its fiscal system on a sounder and more lucrative footing.

IMO the felt anonymity of Reddit, that comes from the fact that hardly anyone cares to remember your username and you don't directly experience scrutiny, isn't that useful. What really matters is the potential for someone to look over everything you've written (and if they have administrator access, connect that to IP, email, browser fingerprint etc.), and use that information for their own purposes, regardless of their having any connection to or legitimate personal interest in you. In that respect, Lemmy isn't much better (it kind of can't be when the premise is publicly posting writing to the internet), but it isn't worse either.