Assuming everything is public, on one hand, can help develop better practices, but, on the other, can lead us to stop fighting for our privacy, so I’m always cautious with it.
About the upvotes/downvotes, they give a lot of information about you, and your pattern can be so unique, that a new account could be identified by it. It can also be used for doxing. Having public votes can also lead to metadrama, just like happens in places like facebook with their like system. And don’t forget that it takes just a small mistake to have your identity leaked, and then you have this data available and tied to your person, exposing your psychological behavior and positions on every theme.
Another thing worth mentioning is the email used to join lemmy. This is basically public, eliminating the expected anonymity from a lot o people (remember, most people aren’t tech-savy enough to create a fake one). In time, bots and trolls will become more common and most instances will probably ban fake or temporary emails, forcing the users to use real ones.
It all might not be a great issue now, when we’re small, but if we expect to grow, I think these things will need to be addressed at some point.