Lemmy has many privacy problems that have nothing to do with public comments you make. For example, the “hide posts that you have already read” option requires that the server track what posts you have read. There is no public activity involved in reading a post. So the Lemmy server should not track that info. If that feature is to exist at all, it should be implemented purely on the client. The same can be said about subscriptions, and for that matter about voting (server should discard voting info after a brief interval for abuse detection). The Lemmy software in many ways naive about this stuff.